Diving deeper into the latest XenDesktop 7.5 IOPS results

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.

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

From the virtual mind of Virtual Feller


Latest XenDesktop 7.5 IOPS

It is amazing when you’ve been focused on a technology for so long that you start to see major improvements. In 2010, I provided my original guidance on XenDesktop IOPS. Four years later, have we seen any major improvement? See for yourself.

As you might be aware, I’ve been working with the Citrix Solutions Lab on validating standardized designs. These validated designs are published as Citrix Design Guides. Part of this latest round of testing with XenDesktop 7.5 and XenApp 7.5 was focused on the new Provisioning Services write cache option “RAM Cache with Overflow to Disk”. When looking at XenApp 7.5, we observed some astounding results, as detailed in the following blogs:

In addition to these, Dan Allen also released a blog on “Turbo-Charging Your IOPS – Part 2” that showed additional impressive results.

But back to the Solutions Lab testing… I’ve finally started going through the results from the XenDesktop 7.5 portion of the test. And what we see is even more amazing than the XenApp tests (which were impressive).

Using the medium workload from LoginVSI 4.0, we observed the steady state IOPS following:

  • MCS: 10 IOPS
  • PVS with Disk Cache: 9.2 IOPS
  • PVS (RAM Cache with Overflow to Disk): 0.09 IOPS

And before you ask, we saw very similar results with vSphere 5.5

We used Windows 7 virtual machines with 2 vCPU and 2.5 GB of RAM (512MB was defined for the RAM cache)

With this one feature within Provisioning Services, we got steady state IOPS to be less than 1/10th of an IOPS without any special configurations. Impressive

The main challenge I see is how the Provisioning Services team will improve upon this. All I can say is “Good luck!”

From the virtual mind of Virtual Feller