Understand  Write Cache feature in Provisioning Services Server

Instructions

Write Cache in Provisioning Services Server

In PVS, the term “write cache” is used to describe all the cache modes. The write cache includes data written by the target device. If data is written to the PVS server vDisk in a caching mode, the data is not written back to the base vDisk. Instead, it is written to a write cache file in one of the following locations:

• Cache on device hard disk
• Cache in device RAM
• Cache on device RAM with overflow on hard disk
• Cache on server

When the vDisk mode is private/maintenance mode, all data is written back to the vDisk file on the PVS Server. When the target device is booted in standard mode or shared mode, the write cache information is checked to determine the cache location. When a target device boots to a vDisk in standard mode/shared mode, regardless of the cache type, the data written to the Write Cache is deleted on boot so that when a target is rebooted or starts up it has a clean cache and contains nothing from the previous sessions.

If the PVS target is using Cache on Device RAM with overflow on hard disk or Cache on device hard disk, the PVS target software either does not find an appropriate hard disk partition or it is not formatted using NTFS. As a result, it will fail over to Cache on the server. The PVS target software will, by default, redirect the system page file to the same disk as the write cache so that the pagefile.sys is allocating space on the cache drive unless it is manually set up to be redirected on a separate volume.

For RAM cache without a local disk, you should consider setting the system page file to zero because all writes, including system page file writes, will go to the RAM cache unless redirected manually. PVS does not redirect the page file in the case of RAM cache.