How to Determine IOPS for Mac OS X


Following up on my previous article of IOPS: Performance Capacity Planning Explained”, this post will cover how to determine IOPS from Mac OS X.

A question that I’m seeing asked more often comes from Apple consultants, who have customers that want to replace their older Apple Storage Arrays with a Synology XS Series. However, before these consultants can proceed with the storage migration, it is necessary to determine the IOPS of the existing array; this article will demonstrate how to determine IOPS from Mac OS X.

Determining IOPS from Mac OS X
Viewing IOPS from Mac OS X

To determine the number of IOPS being utilized by Mac OS X, proceed with opening the Terminal App from / Applications / Utilities. Then proceed to type the following commands:

  • # mount
    • This will determine which disk to get the IOPS data on, in this example, since I want to view the IOPS on the iSCSI Target, the disk target name is /dev/disk1s2
  • # iostat –d disk1 1
    • “iostat” is the name of the program used to gather IOPS data
    • “-d” will display device utilization
    • “disk1″ is the disk that is to be examined
    • “1” is the interval, meaning, report every 1 second

Referring to this image, I’m conducting a file copy of moderately sized movie files to my iSCSI Target on the DiskStation. In the Terminal App, we can see that the average sized per transfer (or IOP) is about 1MB, with about 50-70 Transfers per Second (or IOPS). So, in this example, the storage array is utilizing 50-70 IOPS using a 1MB IOP Size.

The information here is posted to help veteran Apple Storage Admins get a start on learning how much performance their storage arrays utilize, so admins can plan for future storage expansion. This information will aid the decision of what hardware is needed to adequately serve the needs now, and allow for future expansion when increase demand is placed on the storage array.