Recently, while deploying a 50 user pilot of XenDesktop 5 and PVS 5.6 we ran into an issue wherein the install was failing with the following error:

Exception of type System.Data.SqlClient.SqlException caught, error=MODIFY FILE failed. Specified size is less than or equal to current size.

The cause of this error is the PVS database being larger than 20 MB at the time PVS is installed. In this case it was caused by the MODEL database being configured with a fixed size of 500 MB on the target SQL 2008 R2 Server.

Near the end of the install PVS attempts to "increase" the size of the database to 20 MB. I assume this is because it is preparing to insert significant amounts of data (around 20 MB) and proactively increases the database size to avoid the overhead and continually growing the data file. Of course, if they database size is already greater than 20 MB as it was in this case this operation will fail as it is actually attempting to shrink the size of the database.

Our solution was to temporarily reduce the size of the MODEL database while the PVS install was completed. Other workarounds are detailed here in this <a href="http://support.citrix.com/article/CTX127403">KB Article from Citrix.</a>

It would be a better model for the installer to first check the size of the database and then increase it only if it is not already 20 MB.