Overview
This blog post will explain some of the major detailed differences between various hard disk driveRef: 1 (or hard drive, “HDD”) classes and technologies available on the market, as well as what considerations are needed when selecting a hard drive for storage. I admit this post is a lengthy read – but it contains valuable information about the various factors when it comes to looking for a hard drive to purchase.
Table of Contents
- Attributes of Hard Drives
- What’s the difference between Enterprise-class and Desktop-class Hard Drives?
- Which hard drive brand is better?
- Tips for selecting a hard drive for use with the Synology DiskStation NAS
- Which drive to purchase for the Synology DiskStation NAS?
- Applications for ECDs is where reliability and availability are preferred over affordability
- Applications for DCDs is where affordability is preferred.
- Should I use the latest and greatest sized hard drive or use a drive that has been around on the market?
- Using Volume Complete Consistency Check
- Use a UPS
- Summary
- References
Situation
Here are the most commonly asked questions by our users when considering a Synology DiskStation NAS.
- What hard drive should I use with my DiskStation?
- What is the difference between these hard drives?
- Is one hard drive brand better than the other?
Given all these questions, I’ve compiled a list of common questions that were asked about hard drives and will explore the answers this blog. At the end of the blog, I’ll make suggestions about which hard drives to use for which application.
Attributes of Hard Drives
How does spindle speed affect hard drive performance?
Often asked is whether different spindle speeds affect transfer speeds, to which the answer is not appreciably. This is because spindle speeds mainly affects how fast the hard drive will find given a sector. Once the sector has been found, the reading/writing speed of the data will remain consistent, at least for the sake of this discussion.
- To satisfy my curiosity about the performance difference between energy-conscious HDDs versus the standard performance HDDs – a while ago, I conducted a performance test between the WD10EACS and the WD1002FBYS. The results of the performance test resulted in a less than 3% difference while using the two drives, and for handling throughput performance testing, less than a 3MB/Sec difference. While it’s a measurable performance difference, it’s not much in everyday environments as fully saturating a DiskStation’s bandwidth capabilities seldom occurs on a daily basis.
- Where 7200rpm drives will show greater performance over the energy-conscious drives, is in improved IOPS performance. Higher RPMs on drives will lower the reaction time, or “seek time”, of a drive to find a sector – and using the previous theoretical mechanical math formula for calculating IOPS,Ref: 2 we can see that having 7200rpm drives will greatly improve the IOPS performance.
- WD10EACS, assuming 5400rpm (I assume 5400rpm for Western Digital drives that features
variable RPMIntelliPower technology. This reason is that Western Digital originally stated that these drives has spindle speeds between 5400-7200RPM or does not specifically disclose the RPM valueRef: 4, and I’m assuming the worst for my math), has a theoretical mechanical IOPS of 60 IOPS, whereas the WD1002FBYS has 80 IOPS. Having higher spindle drives will affect IOPS performance, useful for database applications (such as MySQL usage), or in Virtual Storage Applications (such as iSCSI, and NFS) as these applications are more IOPS driven, than throughput driven.
- WD10EACS, assuming 5400rpm (I assume 5400rpm for Western Digital drives that features
Are energy saving hard drives worth it?
- To compare the difference between a regular hard drive and an energy-conscious drive, let’s pick two Desktop-class drives (DCDs): the WD10EALXRef: 3 which spins at 7200rpm and the WD10EARSRef: 4 which
spins at a variable rateis optimized for energy-conscious applications. In my theoretical SMB scenario, the drives are spending a cumulative total of two hours a day conducting read/write access, and idling for six hours.- During access, the energy savings for the Green Drive is 1.5 watts. While idling, the energy savings is 2.8 watts.
- Assuming 8 hours a day, 5 days a week, 52 weeks out of the year, the energy savings is 5.1kWh per year. Assuming that energy costs $0.1176 USD/kWh,Ref: 5 the yearly energy savings when comparing these two drives is $0.60 USD per year, when using the WD10EARS.
- To compare at Enterprise-class drives (ECDs), I’m going to select the HUA5C3030ALA640Ref: 6 and the HUA723030ALA640,Ref: 7 where the access energy savings is 5.1 watts with the HUA5C3030ALA640.
- As these drives are intended for Enterprise usage – we can assume 24 hours a day, 7 days a week, 52 weeks out of the year – the energy savings is 44.5kWh a year. 44.5kWh of saved energy equates $5.23 USD saved per year per drive.
- Using the same SMB scenario applied to Hitachi example – then 24.6 watts would be saved each day when comparing the two. This equates to 6.3kWh saved per year, which saves about $0.75 USD.
- What this means is that energy savings are very possible when using energy-conscious drives. However, it will be up to the Storage Administrator to evaluate what is more important: Saving time for processing data, or reducing total operating costs.
- Besides the direct energy savings by the drives, there are also secondary energy savings when cooling systems are considered. Energy-conscious hard drives produce less heat – and therefore, require less cooling, which ultimately lowers operating costs in the long term.
- The data reflected here primarily applies to large-scale systems where hard drives are operating all day. As these hard drives are operating all day – the energy savings from energy-conscious hard drives are appreciable and can quickly lower total operating costs. On a smaller scale, because there are fewer drives used and less operational time, there are fewer benefits.
Do I need SATA 6Gbit/s for better performance?
- Often asked is whether SATA 6 Gbit/sRef: 8 mechanical drives will perform better than a SATA 3 Gbit/s mechanical drives, because the interface between the drive and the host controller is wider with SATA 6 Gbit/s. The answer is no. The reason is that mechanical drives can hardly even saturate SATA 3 Gbit/s, which means that having a 6 Gbit/s interface will make no practical difference. If we take 3 Gbit/s, that’s 3,000 Mbps, add in 8b/10b encodingRef: 9 overhead, which results in 2,400 Mbps of available bandwidth, which equates 300 MB/sec! While there is a hard drive on THG’s chartsRef: 10 that almost breaks 210 MB/sec in a controlled lab environment, but there is no mechanical drive that can even come close to fully saturating 300 MB/sec.
- SATA 6 Gbit/s is best used with a high performance drive, which is mainly the SSD,Ref: 11 where this technology can take advantage of SATA 6 Gbit/s. I would say that even if utilizing this interface, within the DiskStation, in terms of performance, the bottleneck would become the network port of the DiskStation, which is commonly 1GbE.
- As SATA 6 Gbit/s is backwards compatible with SATA 3 Gbits/s, a hard drive with SATA 6 Gbit/s interface installed within a SATA 3 Gbit/s controller will simply operate at SATA 3 Gbit/s capabilities.
- Essentially, with today’s SATA hard drives, and given the application of general-purpose data storage, the interface and hard drive is fast enough for today’s applications. Attempting to make the pre-requisite that everything must be SATA 6 Gbit/s in computer hardware, even though no mechanical device can appreciate that bandwidth, or there’s often other limitations in the computing device; is in fact a waste of money and resources.
Do I need NCQ capable hard drives?
- TCQ or Tag Command Queuing,Ref: 12 allows an OS to send multiple requests to a hard drive and the hard drive can sort out the requests and get them processed. Before TCQ – the OS itself had to arrange the requests and commit them one at a time to the hard drive, hindering the OS’ productivity. SATA’s NCQ technology is much more efficient for handling bulk commands to be processed within a hard drive.
- NCQ or Native Command Queuing,Ref: 13 allows for bulk commands within a HDD to be internally optimized for the most efficient read/write operation of those commands, in an effort to minimize seek time or rotational latency for a platter to be in position to receive those commands. NCQ is mainly beneficial in environments where there are numerous transactions occurring concurrently, such as Virtual Storage, or Database Environments. Most drives today that I’ve seen are NCQ capable and the DiskStation can take advantage of this technology.
Are SSDs the better choice over hard drives?
- This was asked to me in a recent discussion I had with resellers – and in my opinion, SSDs are not a superior option. When compared to $100 USD per Terabyte, SSDs are expensive when it costs about $1000 USD per Terabyte. SSDs can still share same firmware concerns as their mechanical brethren.
- In my view, in the Enterprise market – SSDs are better suited towards data caching or high-speed data access. I wouldn’t recommend using SSDs for handling constant heavy IOPS, given the concern that NAND FlashRef: 34 can only be written a certain amount of time before it fails. In contrast – the hard drive doesn’t have specific limits of how many times data can be written to a specific sector, however, it can still suffer mechanical problems that can cause data loss. Typically, with SSDs, firmware errors are the common problem that can cause data loss. Both technologies must be used properly in a storage ecosystem to tap the best potential out of both technologies.
What’s the difference between Enterprise-class and Desktop-class Hard Drives?
Another frequently asked question is “What is the difference between the DCD and ECD, and where would ECDs would be most beneficial?” From reading the various datasheets out there, I have surmised that the following factors are most importance between the two different classes. These factors will show where ECDs are superior and worth considering for usage.
Spindle Shaft Design difference between ECD and DCD
- On ECDs, typically, the Spindle Shaft is mounted at the top and bottom of the drive, to stabilize the entire spindle when spinning at high RPMs. This method of securing the Spindle Shaft can be found on Western Digital’s StableTracRef: 14, 32 or Seagate’s TCA.Ref: 15 With the Spindle Shaft mounted in this fashion, the platters themselves remain flat when viewed laterally. This in turns, keeps the platter “relatively” in place when viewed from the read/write heads which allows for a constant and consistent flow of information. When compared to their DCD counterparts, because the Spindle Shaft is secured at both ends, the hard drive itself doesn’t have to waste as much time to recalculate the relative position of the platters as the drive spins or re-request the data. Hard drives without this technology may wobble much like the children’s toy topRef: 16, which typically results in performance degradation.
Reliability Design between ECD and DCD
- Power-On-Hours (POH)
- Typically with ECDs, these drives are designed and rated to operate 24 hours a day, for every single day in the year,Ref: 7,14,17 which equates 8760 hours out of each year. ECDs are often manufactured with more advanced techniques or superior internals, which allow them to operate for greater lengths of time.
- With DCDs, they are not intended to operate for that long – Seagate documented the POH on one of their DCDs to be 2400 hours a year.Ref: 18 I would believe that other drives will have similar tolerances – with the exception of Hitachi’s 7K4000 Deskstar drive, given that it has the same POHRef: 19 life as their Ultrastar.
- Exceeding this limit will impose greater wear on the drive, and can result in premature drive failure.
- Annualized Failure Rate (AFR) / Mean Time Between Failures (MTBF)
- AFRRef: 20 and MTBFRef: 21 are statistics which are related to each other – more so with AFR being related to MTBF. These numbers are used by manufactures to state the reliability of the hard drive, often the lower the AFR, the lower chance of failure. Typically, ECDs feature a lower AFR than DCDs. Note that there is no manufacturer of any hard drive that can absolutely guarantee zero down time. I would like to cite Google’s hard drive studyRef 22 conducted in 2007.
- Within their study, they found in general, that the AFR for drives within their first year is 1.7%, and well over 8.6% for drives older than three years. Its meaning reminds me of an old adage: “There are two types of hard drive owners, those who have experienced a drive failure, and those who will experience a drive failure.” I am a member of the former group.
- AFRRef: 20 and MTBFRef: 21 are statistics which are related to each other – more so with AFR being related to MTBF. These numbers are used by manufactures to state the reliability of the hard drive, often the lower the AFR, the lower chance of failure. Typically, ECDs feature a lower AFR than DCDs. Note that there is no manufacturer of any hard drive that can absolutely guarantee zero down time. I would like to cite Google’s hard drive studyRef 22 conducted in 2007.
- Unrecoverable Bit Errors (UBE)
- UBE Rates how many errors will be encountered per read or write operation on the drive, depending on how the manufacture rates it. It can be interpreted as a measurement intended design of how reliable a drive platter is. Typically with DCDs, the UBE rating is typically 1 x 10E14, while ECDs have a UBE rating of 1 x 10E15.
- What this means is that ECDs are ten times less likely to encounter a read or write error, given their greater standards in manufacturing technology.
- ECDs are manufactured with superior internal components and process when compared to DCDs, so they are less likely to have mechanical failure. However, this does not make ECDs invulnerable to failure.
Sector recovery behavior difference between ECD and DCD
- Often with ECDs, manufacturers will advocate another important technology for RAID environments: that these hard drives can recover from defective sectorsRef: 23 faster – thus, maintaining communication and availability to the host bus adapter (HBA).Ref: 33 The most public of these technologies is Western Digital’s Time-Limited Error Recovery (TLER).Ref 24 There’s also Seagate’s Error Recovery Control (ERC),Ref: 25 Samsung and Hitachi use Command Completion Time Limit (CCTL). All of these technologies achieve essentially the same thing, which is to limit how long the hard drive attempts to remap a defective sector, when it encounters one.
- If a DCD in a RAID environment encounters a defective sector, then the drive will spend some time trying to repair that sector, more time than an ECD. During this process, the hard drive can become unresponsive to the HBA, which results in performance degradation. Eventually, the drive will be ejected from the array, as it has stopped communicating for too long, and the HBA believes the hard drive is defective. This will unnecessarily require that the drive be reintegrated into the array which results in the process of rebuilding/resynchronizing the volume to ensure the data is consistent.
- Using an ECD drive will avoid this problem of the drive being ejected from the array due to defective sectors, and lost data from a defective sector can be rebuilt using the redundant mirrors or parities of data on the other drives. Using ECDs will maintain high-accessibility of the volume in large multi-drive Enterprise environments by reducing the interruptions caused by defective sectors.
- Of note, since DSM 2.2Ref: 26, released in September 2009, Synology introduced their own sector recovery subroutine operating in the background, called Dynamic Bad Sector Recovery, to “further enhance the system reliability” with hard drives. This function basically operates in conjunction with DCDs or ECDs, to help maintain availability of a volume when encountering defective sectors on hard drives.
Warranty differences between ECD and DCD
- Most ECDs, given their higher grade of internals, typically come with a 5 year warrantyRef: 7, 14 from the manufacturer, whereas DCDs can come with 2 or 3 yearRef: 4 warranty.
Which hard drive brand is better?
- With regards to which brand is better, in my view, there is no absolute best brand. Based on my experience of using hard drives since 1991 – I’ve experienced hard drive failures from Fujitsu, Hitachi GST, IBM, Maxtor, Quantum, Samsung, Seagate, Toshiba, and Western Digital. In my opinion, as a hard drive is man-made mechanical device, there are bound to be failures. The fact is hard drives are not an infallible piece of technology; the best way to avoid headaches with hard drives is to maintain a good backup strategy.
- I’ve experienced hard drive failure within two minutes of opening a fresh drive (that came in standard 20-drive pack, no less), where the drive resulted in the Click of DeathRef: 27 – and then I have drives that are over 10 years old and are still operating just fine today within my AV and computer equipment at my house.
- What this means is that there really is no best drive manufacturer – it’s not a matter of if a drive will fail, it’s a matter of when a drive will fail.
Tips for selecting a hard drive for use with the Synology DiskStation NAS
Which drive to purchase for the Synology DiskStation NAS?
- Assuming that we’re not talking about capacity requirements, it’s always best to use a drive that Synology has listed as compatible, as referenced on the hard drive compatibility list.Ref 29 Drives listed here have been acquired by Synology and gone through Synology’s testing procedure, which tests for over 70 different parameters – some of which include
- How does the drive behave when it is pulled out of the array?
- How does the drive behave with SMART?
- How does the drive handle defective sectors?
- How does the drive behave when at various ambient temperatures?
- How does the drive handle multiple numerous reboots?
- …and other parameters.
Applications for ECDs is where reliability and availability are preferred over affordability
- One application for ECDs is serving the needs of many users at once – where data inaccessibility due to drive failure will affect many users at once. Where many users’ inaccessibility of data stored on a hard drive can result in thousands of dollars lost per second due to loss productivity, sales and or both.
- ECDs are also intended for handling consistently high IO/s concurrently – such as hosting storage for a database server, or Virtual Storage environment
- ECDs are also used where data needs to be accessible at any given time of the day, 24 hours out of the day, throughout the entire year.
Applications for DCDs is where affordability is preferred
- DCD applications include serving the needs of a small number of users (or even a single user) – who occasionally need to access the drive. Where this type environment can tolerate down time of a few days as they are not fully dependent on that drive for storage.
- Where the drive will spend most of the time in drive hibernation
- As a backup storage
- As an example, I have DCDs at my house for my backup DiskStation. This particular system is only active two hours a day, just to run the backups. The rest of the time, it is in drive hibernation. This is a perfect example of where to apply DCDs.
Should I use the latest and greatest sized hard drive or use a drive that has been around on the market?
- Personally, I don’t use the latest sized drive – as I consider it to be bleeding edge technology.Ref: 29 Usually with any bleeding edge technology, whether it’s a drive, program, computer software, or even a smart phone – there may be some issues that cannot be tested or found within a controlled lab environment. Because of this unknown factor, I usually lean towards older drive technology. I value reliability and affordability within reason. With that being said, as today’s largest size drive is 4TB, I would be more comfortable using a 3TB or even 2TB drive, as 2TB technology has been on the market for a couple of years.
- Another advantage to using older drives is that they are typically more affordable than newer capacities. When more storage is needed – assuming that the DiskStation has a redundant RAID volume, the storage within the DiskStation can be expanded by adding more drives, or swapping out older capacity drives with larger ones.
Using Volume Complete Consistency Check
- When building a volume with in the DiskStation, please always use complete consistency check. While complete consistency check does require more time up front to build the volume, the disks are being stressed by the DSM to ensure that they do not have defective sectors. I would rather take more time up front to setup my volume correctly in the beginning rather than to deal with no-availability or volume errors down the road.
- When using a DiskStation, I always a recommended the use of a UPSRef: 30 to reduce the chance of data loss. As today’s hard drives typically come with 64MB of cache, using say a DS1512+, that would be 320MB of data using a 5-drive configuration. If the DS1512+ were to experience an unsafe shutdown, that would mean 320MB of cached data would be lost from the hard drives. Along with 320MB of data loss from the drives, 1GB of data will be lost from the DiskStation’s RAM. That much data lost can result in data corruption on the DiskStation. A UPS is rather affordable, some that reach as low $50 USD. It’s a small investment to avoid wasting time with handling restoration from backups, or paying several thousands of dollars per hour for data recovery services.
Summary
Given all that has been discussed, I hope that I’ve answered all of the common questions of what is there to know about hard drive technology. In general, when I choose a drive, I usually refer to the Synology HDD Compatibility list, identify the capacity that I need, and select a drive that meets my budget and those capabilities I want it to have. Again, by being conservative with drive selection, I would use a drive size or model that has been on the market for a while, as the market itself has proven that drive reliable. Even after I chose the drives for my project, I shouldn’t become complacent about making backups.Ref 31
References
1. Wikipedia: Hard Disk Drive
2. Synology Blog: Synology XS Series with 100,000 IOPS and 1000MB/Sec
3. Western Digital Caviar Blue Datasheet
4. Western Digital Caviar Green Datasheet
5. United States Energy Information Administration
6. Hitachi GST Ultrastar 5K3000 Datasheet
7. Hitachi GST Ultrastar 7K3000 Datasheet
8. Wikipedia: Serial ATA
9. Wikipedia: 8b/10b Encoding
10. Tom’s Hardware Guide: Charts, benchmarks HDD Charts 2012…
11. Wikipedia: Solid-State Drive
12. Wikipedia: Tagged Command Queuing
13. Wikipedia: Native Command Queuing
14. Western Digital RE4 Datasheet
15. Seagate Constellation ES.2 Product Overview
16. Wikipedia: Top
17. Seagate Constellation ES.2 Datasheet
18. Seagate Barracuda Datasheet
19. Hitachi GST Deskstar 7K4000 Datasheet
20. Wikipedia: Annualized Failure Rate
21. Wikipedia: Mean Time Between Failures
22. Failure Trends in a Large Disk Population
23. Wikipedia: Bad Sector
24. Western Digital: Difference between Desktop edition and RAID (Enterprise) edition drives
25. Seagate: What is Error Recovery Control?
26. Synology Inc: DiskStation DS508 Release Notes
27. Wikipedia: Click of Death
28. Synology Inc: What hard drives does Synology Product support?
29. Wikipedia: Bleeding Edge Technology
30. Wikipedia: Uninterruptible power supply
31. Synology Wiki: What is a Backup?
32. Western Digital: StableTrac
33. Wikipedia: Host adapter
34. Wikipedia: Flash memory
Trademarks
Throughout this article, trademarked names and or descriptions are used. Rather than put a trademark symbol in every occurrence of a trademarked name, I state I am using the names only in an editorial fashion, and to the benefit of the trademark owner with no intention of infringement of the trademark.
Or you can include a good drive and ship it at a discount using your economy of scale.
WHY BORDER US.
Greetings epoon
The DiskStation is sold without drives to provide you with flexibility in choosing your own storage options and budget.
Hope this answers your concerns!
“When using a DiskStation, I always a recommended the use of a UPS…”.
My DS411j has one of those hateful little power bricks.
If UPS is recommended, why don’t you at least make a virtue of this, and make a little UPS that would replace the power brick? At least then, you wouldn’t need AC-to-DC to store power in the battery, and DC-to-AC to send to the brick, which then does AC-to-DC for the NAS. Just one set of AC-to-DC to both charge the battery & power the NAS. Switch straight from AC to the battery when you lose power. Looks like it needs 12v, which is perfect for a lead/acid battery, I think.
For the 411j, which I presume is more of a home/SOHO product, this only needs enough power to safely shut down the NAS – 5-10 mins?
cheers, Martin
PS nice article, BTW. Good info.
Oops – “this only needs enough energy to safely shut down the NAS”.
cheers, Martin
Greetings MP99
Thanks for your feedback – I can see merit in your idea. However, integral UPS system will most likely raise the retail price of the DiskStation, and I would see this potential idea applied to larger systems, such as future rack-systems.
As I’m not a member of our hardware engineer team, I’ll forward your suggestion to them; but I would ask that we keep the discussion to the topic at hand.
Hope this helps.
Nice and comprehensive article.
There is one addition you could perhaps consider: it is deemed best practice to mix brands of drives of the same times, as to limit the odds of both drives failing at the same time.
Even seagate and western digital have a bad week occasionally.
Greetings Arjan
Thanks for your feedback on the article. With regards to mixing models of drives to avoid concurrent drive failure – my research has shown that there is insufficient data to form a conclusive argument where mixing drives is preferred over using drives of the same model or where using the same model of drive is a superior strategy against concurrent drive failure.
Personally, I’ve always used drives of the same model to maintain consistency of data communication throughout the entire array. If possible, I would try to buy drives from a different manufacturing batch – but that is difficult in today’s world.
For the strategy of mixing brands/models of drives, at the very least, I would recommend keeping the same speed, cache, and drive size.
With the practice of using the same drive within the storage array, I would use 2-disk redundancy where possible or needed. For the backup arrays, I would suggest using a different brand/model of drive than the primary storage array. This is in part of my experience where a firmware issue affected a large number of models of drives from a single manufacturer that resulted in both the primary and backup storage arrays failing.
Have a good weekend.
Hey Frankin,
thank ou ver much for this very informative article.
I have a question for you regarding the hiberation mode of the DS.
I am wondering what is putting more stress on the HDD hardware. Is it the constant power on or the spinning ups and downs in hiberation mode?
E.g. I have set up the Download Station to check certain RSS-feeds once per hour. If I allow the HDD to power down after 20 min of inactivity the drive would be down for 40 mins and power up again and so on. Or someone is trying to access th SMB shares after e.g. 15min in hiberation mode or …..
Could you perhaps shed some light on this topic? Right now I dont have any hiberation activated because I think that the often ups and downs would be more stressful then the constant up. I am using a Samsung desktop HDD which has accumulated 9445 power on hours since March 2011 and I am wondering if I am putting to much stress on the HDD which this strategy.
By the way I am using the DS110j as home user thinking about an upgrade in the months to come.
Thank you very much in advance and best regards
Seth
Greetings SethDeBlade
With regards to which is more harmful to a HDD, hibernating and spinning up, versus just being on all the time, unfortunately, there is limited or no specific scientific tests which were done on this subject.
All that can be said is traditionally; mechanically speaking is that a HDD, much like a car engine, experiences the most wear during spin up. Concerns of HDD failure during spin-up have been passed down from previous administration teams, when HDD technology was older.
With the lack of scientific data, I can share my personal experience and anecdotal observations from other administrators that I talk with.
First, a bit of background discussion
Strategy for drive hibernation versus full power on
In your case, considering that the drive is being accessed very frequently throughout the day, I would suggest using an ECD and disabling hibernation in its entirety. If you choose to disregard this recommendation, then you will have a higher probability of experiencing a drive failure. Considering that you’re using a DCD – I would believe that you’re somewhere around the 3% AFR for your drive, instead of 1%.
For the case of using drive hibernation, is for admins that “know” their storage usage; for example, at my office, I set the drives to spin down after 2 hours of inactivity on the primary file server, as during the day, they are heavily used. After the office closes – I don’t mind having the drives spin down after their backups have been completed.
Summary
So, to answer your question, it’s a balance of when to use hibernation, or when to use full power on. For servers that are heavily accessed, I would recommend to use full power on. For drives that are just a couple of hours of the day, using drive hibernation can be considered.
Reminder
A drive will fail, it’s just a matter a time; it’s always a good idea to have a backup of everything, regardless of whether using drive hibernation or not.
–Franklin
Hey Franklin,
thank you very much for your efforts and the additional explanations.
I think I might need another (backup) HDD then. Or perhaps another DS to backup the DS
Best regards
Seth
No problem SethDeBlade, I’m glad I was able to help you out.
Hi,
Next week, I’m buying a DS412+ with all the great reviews it’s had. After reading this I’m looking at 4 x WD30EFRX RED (3TB). Apparently, they are built especially for NAS applications. What do you think Franklin?
Thanks.
Greetings Peter
Hey, congrats on your future purchase of the DS412+, about your question about the WD30EFRX, I haven’t personally used the WD Red Drive. That being said, I haven’t seen any problems with these drives, and recent reviews that I’ve read thus far show that the WD Red drive are quiet, cooler running, and even better performing than other DCDs depending on workload.
You may be interested in reading the following reviews from PCMag.com or StorageReview.com, in which these media publications review a WD Red drive with a DS1812+ DiskStation.
PCMag.com — Western Digital Red Hard Drives
StorageReview.com — Western Digital Red NAS Hard Drive Review [WD30EFRX]
I hope this helps in your decision,
Franklin
Will it be feasible to convert raid volume from Synology Hybrid RAID SHR-1 to SHR-2 or Raid 6 in the future release of the DSM operating system as converting from 1-disk redundant SHR to 2-disk redundant SHR is not available with the current DSM4.1
Greetings VC2010
At this time, converting from 1-disk redundant SHR to 2-disk redundant SHR is not supported; however, it’s something that we’re evaluating for a future release of the DSM. I’ll take your feedback to our developers for consideration.
For now – if you’re looking at needing 2-disk redundancy – you may wish to consider building the volume with 2-disk redundant SHR. And as your budget allows – add additional disks and expand the Volume to use the additional storage pool.
Hope this helps,
Franklin
As I want to improve the fault tolerance with min. cost, creating multiple RAID arrays is possible but not preferable(says SHR-1&SHR-2 requires 3 HD bays while SH-2 only requires 2 HD bays). Do you have any suggestions on changing the existing volume raid type?
What are the pros and cons of using multiple volumes on a single RAID? Will it reduce the amount of time needed to rebuild the volumes(says when only 1 volume fails)? What is the impact on performance?
Greetings VC2010
Here’s my take on the balance between redundancy and storage capacity,
Here’s the supported disk for each RAID level
I’m confused as to where you are reading where SHR-2 requires two disks; can you clarify where you are seeing this?
Multiple Volumes on RAID is also known as a Virtual Volumes, a concept of partitioning out a single RAID Volume into multiple volumes for storage management. This is mainly used for Business Storage Administration – and is not typically used for SOHO or Personal use applications. A Virtual Volume is still dependent upon a RAID volume – therefore, if the RAID volume fails, all Virtual Volumes will fail.
May I ask what DiskStation do you have?
My quote is based on no. of disk redundancy, not min. disk required. (i.e. for SHR-2 or raid 6 ,no. of disk redundancy=2 and min. disk required=4).
Based your recommendation for raid groups and storage capacity, It seems that the ‘practical’ upper limit on the hard drive no. for raid 5 is 8. As I am using ds1812+, I require a raid array which provides a balance of performance, availability, capacity. Raid 5 is less fault tolerant with only a single drive’s worth of redundancy.In comparison, raid 6 is slower but it can improve availability (2 disk redundancy).
Will it reduce the amount of time needed when expanding/repairing a dynamic/ virtual volume (not a raid volume)? When a dynamic/ virtual volume fails, what is the impact on performance consistency of other dynamic/ virtual volumes?
VC2010
Usually with RAID-6, the amount of time to rebuild or expand a volume will be more so than RAID-5 – my experiments show around a 10-20% penalty when using RAID-6 over RAID-5.
Hope this helps.
Hi! Nice article! And finally i found a reason why my DS409+ sometimes pulled-out of RAID5 one of my DCD Seagate drives – IMHO this is due to unresponsivity of one of drives. After disconnecting/connecting same disk to RAID all is ok.
So – here is my question: is there any way to increase time to wait for drive when it relocates bad sector? Maybe with increased timing i finally can reduce occurancy of drive fails!
Hi deksden
There is currently no setting in the DSM which will allow you to increase the timeout value. Note that there is a downside to having a large timout value. Which is if the disk is non-repsonsive while conducting a sector remap, then the DSM is waiting for that disk, that means performance of the DiskStation will be degraded or even data loss can occur (while data is transmitting to/from the DiskStation) because the whole system is waiting for a single disk to respond.
Best way of avoiding sector remap delays is to consider using ECDs, or even consider the WD Red Drives. Another idea is to use complete consistency check when building a volume.
Hope this helps!
Agree – increase of timeout actually is not good idea!
But maybe there is a way to reconnect outed disk into array without physically removing and plugging it back? Because I should be near device to do this, and maybe I can do something remotely? Simply “virtually hard reconnect” or thomething similar?
Greetings deksden
What you’re asking to do typically requires expert knowledge of the Linux Kernel, and is typically more complicated to execute than what the majority of users are looking for. For ease of use, I would recommend that you consider using ECDs for your data storage.
Hope this helps.
Hi,
So the major difference between Enterprise & Desktop appears to be recovery timeout. From what I’ve figured out with WD drives it’s not possible to enable TLER, but I’ve heard people saying that CCTL can be enabled on Hitachi drives. So for me at this point, it’s either WD Red 3TB ($220) or Hitachi Deskstar 7K4000 4TB (0S03355) – not on synology’s compatibility list, I think earlier version was, but it’s only $199 – on sale at Frys.
Can someone please suggest if it’ll be better to go with Hitachi or WD Red. Hitachi has 1TB more storage, but if CCTL cannot be enabled on it, then I probably won’t go with that one.
Thanks in advance!
PS. I’m planning on using it with DS413
Greetings tunafish24
I would recommend that you consider using officially supported drives with officially supported functions. Modifying drives for the storage of your data is not a procedure I would recommend.
Have a good day.
Thanks Franklin…Actually I called Hitachi and they said that Model#0S03355 is the same drive as the one you listed (0S03363) as a compatible drive for DS413 – the later model is sold as part of 20-pack, but essentially same drive/firmware on both.
The CSR at Hitachi also said that the CCTL for this drive is 50 milliseconds. Does it mean that I don’t have to manually set CCTL for this drive? You guys must have done some research on hitachi drives, do they work well with NAS because of low CCTL values? I’m asking this because even if synology NAS uses a software raid and doesn’t drop a drive, if a desktop drive gets in error recovery mode, it still means that it’s repeatedly trying to recover data and will experience degraded performance during that time. Is that true, or does synology send a cancel command to the harddrive to avoid this behavior?
Sorry for missing your reply tunafish24, but to answer your questions;
1. I don’t recommend altering the settings on the drive itself –
2. If the Hitachi drive experiences a defective sector, it will still enter sector recovery mode and attempt to repair that sector. During this time period, the volume performance will be degraded as one of the disks isn’t behaving at its best performance.
Hope this helps.
I recently bought the DS413j right after it was release and I am liking it so far. This has been a good article because I am looking at replacing my hard drives in it (At the moment I am using hard drives that I had laying around).
You said ” Of note, since DSM 2.2Ref: 26, released in September 2009, Synology introduced their own sector recovery subroutine operating in the background, called Dynamic Bad Sector Recovery, to “further enhance the system reliability” with hard drives. This function basically operates in conjunction with DCDs or ECDs, to help maintain availability of a volume when encountering defective sectors on hard drives.”
My question is does the Synology DSM 4.1 Dynamic Bad Sector Recovery tool work in conjunction with the TLER for example on the WD drives? So, basically does Synology support TLER function on the drive?
Hi asnakhla
The Dynamic Bad Sector Recovery Tool works in conjunction with TLER to help reduce the possibility of the drive ejecting from the array due to a sector error. To be precise on how TLER operates, basically requires a True Hardware RAID controller, something typically in the range of 700 USD or greater.
Hope this answers your questions, and have a good evening.
Hi Franklin,
Great article. it really explains a lot. I have a question, though. I recently purchased a DS412+. I originally set it up with a 3 TB drive as a basic disk and did a whole big data dump on it. I then expanded with two additional 3 TB drives, changing the format from basic to Raid 5. The only thing is that when I changed the RAID format, DSM did not give me the option to do a Complete Consistency Check. Did it do it on it’s own as part of building the RAID? If not, is there anyway I can do it now?
Thanks
Hi steve57200
When changing a volume from basic to RAID-5, part of the volume change process is to do a background consistency check, as the disks are being stressed by the storage manager to handle the RAID migration. So, your disks are checked, and should be good to go, as the RAID expansion succeeded.
Hope this helps, and have a good day.
As far as Enterprise vs. Desktop is concerned, I’m still a little confused. i want to use RAID5 and figured I need to use Enterprise class drives. But I read above that you have implemented Dynamic Bad Sector Recovery, to “further enhance the system reliability” with hard drives. Does this mean that it is OK to put Desktop class drives in RAID without fear that a drive may be ejected from the raid set in case of sector error?
cheers
Greetings Rau
The Dynamic Bad Sector Recovery is aimed at reducing the chance of a drive ejection due to a defective sector. It doesn’t preclude from using ECDs where it is needed. I still recommend using ECDs where the environment requires the availability of these drives, or at the very least, consider the WD Red Drive if immediate budget is a concern (and taking the risk of volume errors in the long term).
Hope this helps.
Hi Franklin. I’m new to the Synology world. I recently bought a DS1812+ along with 4 WDRed 2TB drives before I discovered your blog and this great article on the subject.When I will be ready to expand with four more drives, I was thinking of creating a second volume with four drives as SHR-2 as opposed to one big volume with eight drives. I was hoping to reduce even more the possibilty of loosing a large amount of data by splitting the volume in two. Is this a good assumption or is there a down side to do this? Any help would be appreciated. Thanks.
Hi jimmy454
Assuming that you have 2×4-disk volumes in RAID-6, there’s nothing wrong with this configuration. Yes, you’re being more cautious from defending yourself from multiple disk failure, which is perfectly fine. The down side to this configuration is lack of storage usability, as you’re using four disks total to handle the redundancy. Other users may not like this idea, as it doesn’t provide enough usable storage. However, if having 8TB of storage capacity is plenty for you – then I believe you’re fine.
I’ve found all your replies Franklin helpful. I have the Ds1812+, and have 4 drives coming in 3 days that are 3gb each and on the compatibility list. I’ve been looking at doing Shr-2 or Raid 6. Shr-2 looks like raid 6. All the drives are of the same size, and i was wondering if i should do raid 6 over shr-2 or not. If the unit it upgraded in the future to anything above 3gb, it would be different sizes, and then would shr-2 be a benefit? Or should i look at the fact they are all the same size, and will not be changed in a long time? With the same sized drives is there any benefit of shr2 vs raid 6 vs speed/rebuild/etc? Thank you for your time.
Hi kryon5025
If you’re looking at SHR-2 and RAID-6, yes, SHR-2 is based upon RAID-6 technology. If you’re keeping the drive sizes the same, then using SHR-2 doesn’t offer much in term of immediate benefit. However, as your drive size change as you upgrade, that’s where SHR comes in handy, as you’re able to access your new storage pool sooner. You may wish to refer to the “Expanding with larger disks with SHR” article to see how this process is varied between Synology Hybrid RAID and Classic RAID.
The performance difference between SHR and Classic RAID is less than 1% in my lab; the varying drive performance will have a greater impact in term access performance on the DiskStation.
Which RAID type you use is up to you – personally – if the drive sizes are going to remain the same, and that your budget allows you to buy mass quantities of drives at a time when it comes to upgrading storage, I would lean towards RAID-6. The reason for this is that expanding a SHR volume can require more time than expanding a classic RAID volume. If your budget doesn’t allow for that level of flexibility, then I would consider using SHR and incremental storage expansion.
Hope this helps,
Good article and the comment thread adds to the knowledge.
A point about this regarding variable rate RPM “WD10EARS (Ref: 4) which spins at a variable rate”.
As you’ve written it suggests, or might be interpreted, that the single drive changes speed during operation, which it does not do from what I’ve been able to read. “IntelliPower” seems to be “market speak” meaning that drives might have different RPMs – not that the drive changes RPM during operation.
I’m including some links below and would be interested in your thoughts about this – and perhaps clearing up the wording in the article ?
http://www.silentpcreview.com/article786-page2.html
A quote from the article : “For each GreenPower™ drive model, WD may use a different, invariable RPM.”
Hi Gustav
Thanks for the link, I did some background reading to the subject further, and my results is the same as yours. My results thus far show that the IntelliPower Function is not actively changing the spindle speed of the drive. The original term back when this technology first came out, where it says 5400-7200, like others, lead to my belief that the WD Drive is actively changing the spindle rate.
But thanks for the clarification and additional information.
Thank a lot Franklin for this wonderful article and the information you gave in your replies.
Though I did not use RAID before, but from the horror stories I read in the internet about RAID and specially when the RAID controller fails then you will kiss all your hard drives and data goodbye; I decided not use RAID ever (unless you convince me otherwise). Instead it will be enough for me to have the original data in my five PCs in my home, the backup in my NAS, and an offline backup provided by my Broadband supplier.
Now my question is that I intend to buy the Synology DS213+, can I install a 2TB (I will use for data backup) and a 4TB (I will use for all my media; videos, pictures, music, movies, etc.), if so, will they show in my PCs as two drives or single large one.
Many thanks in advance for your kind help.
Hi BenTa
With regards to your concern with RAID, those concerns are typically applied for Hardware RAID controllers, where they feature ASICs to generate the specific RAID parity. The DiskStation uses software RAID; as such, should there be a failure on the DiskStation, the HDDs can be migrated to another chassis and resume. Or if necessary, be installed in a regular Linux computer, and an well-experienced (or professional) Linux storage administrator can access the data.
Just as a side note, the above statement is a reactive procedure; it’s always best to have a backup of your data, as RAID is intended to maintain high-availability of your data during a disk failure, it doesn’t protect it against total multiple hard drive failure or total system failure, should these scenarios occur.
Your strategy of using the DiskStation as a backup, and then backup to your broadband supplier is an excellent backup strategy.
With regards to your question, yes, you may install a 1x2TB and 1x4TB drive in the DiskStation, format them as “Basic” mode, which is a 1-disk volume. From here, you’ll have to create your shares, and store them on their respectful volumes, such as “backup_share” on volume1, and “multimedia_streaming” on volume2.
Hope this helps,
You are a star. Thank you very much for the wonderful explanation and advice, and yes you managed to convince me to use RAID in addition to my backup plan. Many thanks again and wish you all the best.
What about the Western Digital Red drives (NAS class, not desktop, not enterprise). According to Western Digital, these drives are optimized for use in NAS systems, and their price point is quite attractive.
Hi macounwr
I haven’t seen any serious problems or criticism with WD Red Drives; you may be interested in reading the following reviews from PCMag.com or StorageReview.com, in which these media publications review a WD Red drive with a DS1812+ DiskStation.
PCMag.com — Western Digital Red Hard Drives
StorageReview.com — Western Digital Red NAS Hard Drive Review [WD30EFRX]
Using the WD Red Drive is a better choice than Desktop; however, if your application calls for 24/7 heavy access, such as hosting a SQL database, or use for production virtual storage environment, I would still recommend Enterprise-class.
Hope this helps,