As you might have read, I recently ran a few XenServer PVS Accelerator tests to determine a starting point for the cache size.  This initial investigation looked at Windows 10 and Windows 2012R2 for boot and logon operations.

Looking back, I determined that I want to include three additional items

1. Impact of a larger cache size – Increase from 2GB to 4GB RAM cache
2. Impact of applications
3. Impact of Windows 2016

Before I get into the results, let me explain the graphs.

• The blue, green and orange line denotes boot, logon and steady state operations. The first time those colors appear depicts the first VM; the second time the colors appear depicts the second VM. These colors are linked to the axis on the right showing percent of cache used.
• The solid red area graph depicts the amount of network traffic sent from the Provisioning Services server to the host.  The line should initially be large and then diminish as the cache is used. It is linked to the left axis with bytes per second.

With that understanding out of the way, let’s look at the results.

Windows 2012R2

Windows 10

Windows 2016

Observations

First, I find it interesting that Windows Server 2016 sits between Windows 2012R2 and Windows 10 in terms of cache consumption after boot, logon and steady state operations complete. This makes sense as Windows 10 and Windows Server 2016 are considered to be similar operating systems, requiring more cache than Windows 2012R2.  But it also shows that Windows Server 2016 is more optimized, with fewer extraneous apps/services as shown in the Windows 2016 Optimization guide.

Second, even though the size of the PVS Accelerator cache was doubled 4GB from 2GB from previous tests, the overall usage remained the similar.

Third, the biggest cache utilization during logon and the least during steady state. Usage matched expectations based on read/write IO ratios for boot (80% read / 20% write), logon (50% read / 50% write) and steady state (10% read / 90% write). The more unique read IO activity, the more cache utilized.

Based on this round of tests, I’m sticking with my previous PVS Accelerator cache size recommendation and adding Windows Server 2016:

• Windows 10: 2.5GB per image per host
• Windows 2012R2: 2GB per image per host
• Windows 2016: 2.5GB per image per host

Daniel (Follow on Twitter @djfeller)
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