Strange issue consumes disk space on Windows 2008R2 sp1

Recently i was troubleshooting a lack of disk space on Hyper-V host servers and was baffled by the large (50+gb ) of disk space that was missing from the system.

The host servers have modest (read 160gb) Partitions for the DOM0 partition.  I found that VSS in the default setting when disabled in set to “UNBOUNDED” and applications that use VSS, such as ONTAP and Netbackup may create temporary files that need to be cleaned up , and ultimately, you should set the maxsize parameter with vssadmin to avoid this issue altogether.


Start with a command prompt in administrator mode

next run this command to see where your VSS usage is at the moment:

"vssadmin list shadowstorage


the output should look something like this

C:\>vssadmin list shadowstorage
vssadmin 1.1 - Volume Shadow Copy Service administrative command-line tool
(C) Copyright 2001-2005 Microsoft Corp.

Shadow Copy Storage association
   For volume: (C:)\\?\Volume{1f579c24-a50d-11dd-83df-xxxxxxxxxxxxx}\
   Shadow Copy Storage volume: (C:)\\?\Volume{1f579c24-a50d-11dd-83df-xxxxxxxxxxxxx}\
   Used Shadow Copy Storage space: 47.256 GB
   Allocated Shadow Copy Storage space: 49.405 GB
   Maximum Shadow Copy Storage space: 50 GB

If the last line shows “Maximum Shadow Copy Storage space: UNBOUNDED (100%) ” Then your application that is listed as a provider or writer for VSS can and will consume quite a bit of disk space. I found articles from Microsoft that made similar recommendations on the 15% value.


Here is an example of the command you would use to re-size the Unbounded ShadowStorage to a percentage of drive space (this is the recommendation from Symantec for the Netbackup product)


vssadmin resize ShadowStorage /for=C: /on=C: /maxsize=15%

Obviously you can find what drive letter to insert after the /for= by looking at the output from the list shadowstorage command.


And if you are a Netbackup customer, do not set the size lower than 15% as your backups may fail.


The official recommendation seems to come from Microsoft (10%) but i had to increase the size of the shadow storage to avoid “Status Code 156” errors on backup. Other issues may arise from insufficient shadowstorage space such as “Network Read Error”.

Here is a link to Symantec’s KB on the issue



I hope to apply this change to all Hyper-V host servers along with a cleanup of files leftover from sp1 for 2008R2.

Here is the link on how to clean up that leftover backup files and get back 4gb or more: (


Let me know if you have any more disk space hogs that can be safely removed from windows 2008 R2 SP1.


The end result of running these two procedures netted over 250gb of free space on some servers. Your Mileage May Vary…..