In facing the growing demand of virtualization, storage companies are keen to strengthen their support in the area. Until July 9th, 2012, only 19 companies have acquired vSphere 5.0 certification. It’s not hard to conclude that the certification remains a technical barrier for many companies. Even fewer companies hold products that passed VAAI compatibility test.
Not only does DSM 4.1 Beta continues to support VMware vSphere 5.0, it’s also fully compatible with vSphere 5.0 VAAI. The in-depth compatibility enhances the communication between storage device and virtual servers, allowing users to construct a virtualization environment more smoothly. In my previous article, we looked at how ATS was able to allow multiple ESXi servers to simultaneously access a single LUN, a design that’s aimed to minimize process time and enhance efficiency. This VAAI primitive is actually supported since DSM 4.0.
As we developed DSM 4.1, one of the goals is to support other VAAI primitives in order to level up the support in virtualization environment. In the following article, I’ll continue to explain the VAAI primitives and their benefits business can benefit from DSM 4.1 Beta.
Full Copy – Extend Copy
To IT staffs that manage a great number of virtual machines (VM) daily, cloning VMs is a common operation. However the larger a VM is, the longer time it takes to clone. Extend Copy can alleviate this situation by having the action to perform at the storage level. The command specifies the source and the destination of the clone, the chain length, and other relevant information. By having the task to perform at the storage level, the data transfer between ESXi server and DiskStation can be significantly reduced.
Extend Copy increases the efficiency of data write-in. To further enhance performance and relieve virtual server resources, “Write Same” feature is added to vSphere 5.0 VAAI.
Block Zeroing – Write Same Zero
Block Zeroing is developed since vSphere 4.1. This enables storage arrays to zero out a large number of blocks. Initiating VMDK requires lots of zero to be written into blocks, which is a very performance-focused task for ESXi server. Write Same is a SCSI command that instructs storage device on the blocks that need to be zeroed, offloading the tasks onto storage devices instead. This reduces the redundant data transfer between ESXi Server and DiskStation, reserving bandwidth and processing power to other tasks.
Write Same simplifies the original redundant task and releases reserved blocks to be reused. Storage space is utilized more effectively. IT staffs can also create VM in a shorter time.
VAAI Performance test:
The following is the testing environment:
- ESXi Server spec:
- CPU: Intel(R) Core(TM) i5-2400 CPU @3.10GHz 4-Core
- RAM: 8GB RAM
- NIC: Intel 82574L Gigabit x 2
- OS: ESX 5.0.0 504890
- OS hard disk: Hitachi HDS721050CLA662
- MotherBoard: MSI MS-7740 mainboard
We used a DiskStation of XS-series, along with the following spec and settings:
- Disk: WD 2TB WD2002FAEX-007BA x 2
- Disk: WD 2TB WD20EARS-60MVWB0 x 2
- Raid Mode: RAID 5 (4-disk)
- File-based iSCSI VAAI LUN
- File-based iSCSI None-VAAI LUN
Block Zeroing Test:
The test scenario is to compare the time length to create an 80GB virtual machine that requires block zeroing on a VAAI-supported LUN and one that doesn’t support VAAI. On a non-VAAI-supported LUN, the process takes 1,116 seconds to complete. Yet, if the LUN supports VAAI, the process takes only 8 seconds, which is almost 140 times faster than its counterpart. The great difference is contributed by Write Same command. The following is the visual representation on the test result.
We test Full Copy on a virtual machine that consists 10GB of data. The test is to see the time required to clone the VM onto another VM. When cloning onto a LUN with no VAAI support, the process takes 208 seconds. The time is significantly reduced to 6 seconds when the target LUN supports VAAI. The following is the visual representation on the test result.
What do the two tests indicate? Well, cloning a VM and vMotion are two of the most commonly used functions in VM management. A 1TB VM requires 5.9HR to clone, but with VAAI support, the process takes only 10 minutes. So you can imagine how much better off businesses will be with vSphere 5.0 VAAI.
As the variety of IT services evolves, one of the criteria to evaluate a service’s competitiveness is whether the company has embraced virtualization, and to what extent. Judged by this stance, Synology is definitely a very competitive company. Our high-end products fully support VAAI. Users are able to speed up VM creation by using Write Same command to facilitate block zeroing process; ATS function allows an iSCSI LUN to be accessible by multiple ESXi servers at the same time; Full Copy focuses to speed up the time required for vMotion and VM cloning. Companies benefit from more efficient storage utilization and a VMware storage-aware environment.
As more and more companies commit to the support of virtualization, VAAI compatibility can be considered as an indicator to their commitment level and technical capability. In this aspect, DSM 4.1 Beta can be viewed as a milestone in Synology’s continuous development and support.