Cannot find anymore diff area candidates for volume

Challenge

Backup or replication of a Windows OS fails. In the Windows event logs of the machine being backed up, there is an error with ID 8193 from source VSS:

Volume Shadow Copy Service error: Unexpected error calling routine Cannot find anymore diff area candidates for volume \\?\Volume{xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxx}\ [0]. 

Note: This KB specifically addresses the error “cannot find anymore diff area candidates for volume.” There are a variety of possible VSS errors with ID 8193.
 

Cause

The Volume Shadow Copy Service is unable to allocate disk space to create a shadow copy because the maximum size of the shadow storage area is too small.
 

Solution

Note: If this error occurs on a Hyper-V host when backing up VMs on that host, see KB1846.

Increase the shadow copy storage area for the volume listed in the error event, or set the maximum size to “No limit.”

To identify the volume listed in the event, run “mountvol” from a command prompt; below the usage information will be a list of volume GUIDs and their associated mount points, if any.

This size of the shadow storage area can be changed in the Shadow Copies utility, or from the command line.
 

Shadow Copies Utility (Server OS Only)

To access the utility, right click any volume and choose Configure Shadow Copies. On older server operating systems, this may instead be a tab in Properties.
In the Shadow Copies utility:

1. Select the volume with insufficient space;
2. Click Settings…
3. In the “Maximum size” box, either increase the limit, or choose “No limit”.

A limit of 15-20% of the total volume size may be needed on busy servers.
 

Command Line (Client or Server OS)

All commands below should be run from an administrator command prompt.

Use vssadmin list shadowstorage to view existing shadow storage associations. If no association exists for any volume, the command response will be “No items found that satisfy the query.”

Note: When no shadow storage association exists for a volume, the shadow copies utility will display 10% of the volume or MinDiffAreaFileSize, whichever is greater. However, Windows may set a different maximum size during shadow copy creation. While the default behavior works well for most volumes, setting a limit of 15-20% of the total volume size may be needed on busy servers.

If no association is listed for the volume, run vssadmin add shadowstorage to set the size of the shadow storage area. For example, on a 1 TB volume labeled D:

vssadmin add shadowstorage /for=D: /on=D: /maxsize=200GB

If a shadow storage association already exists, run vssadmin resize shadowstorage to set the size of the shadow storage area. For example, on a 1 TB volume labeled D:

vssadmin resize shadowstorage /for=D: /on=D: /maxsize=200GB

The /maxsize parameter is not optional, but can be set as /maxsize=UNBOUNDED


 

More Information

By default, each volume stores its own shadow copy. For example, a shadow copy of a CSV mapped to C:\ClusterStorage\Volume8 would also be stored on C:\ClusterStorage\Volume8. The location of the shadow storage area may be changed as described in KB1794.

It is not necessary to enable shadow copies for shared folders. It is normal for “Next Run Time” to show “Disabled.”