As you saw in a previous blog, XenDesktop 7.5 is able to achieve an average IOPS value of less than 1/10th per user. Of course when you put out unbelievable results like this you hear a lot of comments trying to find holes in the results or test procedures. This is as it should be as it is part of any good scientific method.

In order to show a more complete picture of the value of the new Provisioning Services Ram Cache with Disk Overflow, we gathered additional details from the Citrix Solutions Lab’s tests. This set of data includes details for the duration of the entire test that included logons for roughly 100 users (sorry but it didn’t include boot. However, booting is mostly a read operation that PVS can handle with server-side cache).

The results are still just as stunning as the steady state:

For a physical host, we accumulated IOPS numbers for each of the virtual desktop sessions then combined into a single graph. As you can see, during the logon portion of the test we had a peak, and I mean maximum IOPS value, of 12 IOPS.

What if we don’t break it down by user, what would the host’s total IOPS graph look like?


The absolute peak is 155 IOPS on a host that is running 100 VDI VMs. (If my memory is accurate, I believe a 15,000 RPM drive can do roughly 180 IOPS).

Tests details were as follows:

  • LoginVSI 4.0 medium workload
  • Hypervisor: Hyper-V 2012R2 and vSphere 5.5
  • Virtual Machine: Windows 7, 2 vCPU and 2.5 GB of RAM (512 MB as defined for the RAM Cache)

Based on results like this, I’m left to wonder how many users I can support on my mid-1990s college PC (Pentium 486 with a 420MB hard drive) J

Virtually signing off…