Tag Archives: PVS Accelerator

XenServer PVS Accelerator Sizing – Part 2


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.

Continue reading XenServer PVS Accelerator Sizing – Part 2

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XenServer PVS Accelerator Cache Sizing


How large should we make our PVS Accelerator cache? Too large and we waste resources. Too small and we lose the performance.

Let’s take a step back and recall our best practice for sizing the RAM on Provisioning Services.  We would typically say allocate 2GB of RAM for each vDisk image the server provides.  This simple recommendation gives the PVS server enough RAM to cache portions of the image in Windows system cache, which reduces local read IO. So for a PVS server delivering

  • 1 image:  we would allocate 2GB of RAM (plus 4GB more for the PVS server itself)
  • 2 images:  we would allocate 4GB of RAM (plus 4GB more for the PVS server itself)
  • 4 images:  we would allocate 8GB of RAM (plus 4GB more for the PVS server itself)

Easy.

Let’s now focus on the XenServer portion of PVS Accelerator. If we use RAM as our PVS Accelerator cache, how many GB should we allocate?

Continue reading XenServer PVS Accelerator Cache Sizing

Monitoring PVS Accelerator


I love data. I like seeing numbers and graphs. I like to see if something is having an impact.

I like when new capabilities provides us with the means to monitor because this data gives me reassurance that the feature has an impact instead of me simply believing it does.

Let’s look at XenServer 7.1 and Provisioning Services Accelerator. I was able to show that

  1. PVS Accelerator reduced VM boot times
  2. PVS Accelerator reduced user logon times

But I didn’t have any details beyond what I was able to gather from a stopwatch.

That was until I starting poking around XenCenter. I was thrilled to see a set of metrics specific to PVS Accelerator

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Improving Logon Time with PVS Accelerator


The title is correct.  We can improve user logon time by implementing PVS accelerator in XenServer 7.1.

This actually makes perfect sense.

We already showed that PVS Accelerator drastically improves VM boot times because portions of the master vDisk image are cached locally.  Booting a VM equates to roughly 80% reads and 20% writes.  VMs using the same image are reading the same blocks of data. Due to this similarity, we are able to see huge network utilization reductions by using the PVS Accelerator cache. These reductions in the network utilization translates into faster boot times.

But what about logon time?

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Provisioning Services Accelerator


An interesting new feature was included with the XenServer 7.1 release: Provisioning Services Accelerator.

In a single sentence,

PVS Accelerator overcomes PVS server and network latency by utilizing local XenServer RAM/Disk resources to cache blocks of a PVS vDisk to fulfill local target VM requests.

Take a look at the demo video to see:

Continue reading Provisioning Services Accelerator