I have an enviroment for automated testing where I configure 40 VMs (20 Windows 7, and 20 Windows Server 2008 R2) for testing. Each VM is cofigured to use a differentiating VHD out of an template VHD. After some basic configurations is made on the Differentiating
VHD we snaphot de VM. This snapshot is the starting point for our tests.
We use the differentiating VHDs to save disk space ( we use around 1/3 of the normal amount we would use with dynamic VHDs). The snapshots are used to get to starting point for our automated tests. We want to Always start from the same point and we test
our application several times a day.
Here is the issue:
I've noticed this week that after I revert the snapshots on the VMs, the System Process (PID 4) start having lot of disk activity on the .AVHD files. In between 100-400 MB/s. It varies a lot. The AVHD. files on the Windows 7 VMs goes from around 500
MB after snapshot restore to 14 GB. This goes on for several munutes. After some time it stops.
The VM is idle and doing nothing. This disk activity is affecting a lot the install times of our application on the VMs. Normal install time is around 1 minute on SSDs, but due to this disk activity it's taking up to 16 minutes. Whe this thing stops, install
times goes back to around 1 minute.
Physical server has 192 GB Memory, 2 SSDs in RAID 0 and dual 6c XEON E5-2632 v2 @ 3.5 GHz processors. It's running on Windows Server 2012 R2.
The issue beeing, why does PID 4 do so much activity and increase de AVHD file while the VM is doing nothing?