How to Use VSSADMIN Commands To Manage Low Disk Space

Low disk space alerts are a common occurrence in I.T. For SQL Server consultants, there could be a few causes:

• A runaway transaction filling up a log file or even an mdf file in a user database or tempdb.
• Someone or some process took an extra backup that wasn’t planned for.
• A new database was created with larger than expected files sizes.
• An application is using the Volume Shadow Service to make backups of databases to a local volume.

This last scenario related to volume shadow service is what I want to talk about today. This one can be a little confusing at first because your organization may get a low disk space alert that doesn’t seem to make sense. The alert may indicate that there is less than 10% free space, but looking at the volume in Windows Explorer doesn’t show that at all. It turns out that VSS files aren’t visible to Windows explorer. You might come across this when investigating the following error, “Volsnap – 36 – The shadow copies of volume E: were aborted because the shadow copy storage could not grow due to a user imposed limit.”

To investigate what is happening, try some of the VSSAdmin commands, like this:

vssadmin list shadowstorage

The output pf this PowerShell command will show what volumes are being backed up by VSS, and what the target volume is for those VSS files. If the volumes are already low on space, deleting some of the shadow copies may be the first thing needed. This can be done with the following command:

vssadmin delete shadows /for=<ForVolumeSpec> [/oldest | /all | /shadow=<ShadowID>] [/quiet]

Then a limit can be placed on the amount of storage allocated to VSS files using this command:

vssadmin resize shadowstorage /for=<ForVolumeSpec> /on=<OnVolumeSpec> [/maxsize=<MaxSizeSpec>]

Keep in mind that someone will need to determine first if the older VSS files are needed prior to executing the delete and resize commands.

Tired of Chasing SQL Server Alerts?

Dealing with disk space issues on your SQL Servers? That’s exactly the kind of problem The SERO Group solves every day. Schedule a free discovery call and let’s take a look.