Beta testers and even MS employees often ask us why restore points take up so much disk space and whether this can be adjusted. I also see the opposite problem reported—testers are surprised that so few restore points are being kept on the system. The best way to see what’s going on is to use the vssadmin tool from an elevated command prompt. I’ll walk you through how to do this.
But first, let me clarify some terminology: I use the terms shadow copy and restore point throughout this article. Restore points are a special type of shadow copy because they store specific information needed during a system repair with System Restore. Restore points are created by:
Shadow copies created on the Complete PC target volume are not restore points. However, both types of shadow copies can exist in the same shadow copy storage area at the same time.
Let’s take a look at how big the shadow copy storage areas are on my computer running Windows Vista. The shadow copy storage area is where shadow copies are stored on each volume.
I ran the vssadmin list shadowstorage command (from an elevated command prompt) to obtain this output:
V:\Windows\system32>vssadmin list shadowstorage
vssadmin 1.1 - Volume Shadow Copy Service administrative command-line tool
(C) Copyright 2001-2005 Microsoft Corp.
For volume: (C:)\\?\Volume{3ce0cbe2-57c2-11db-a712-806e6f6e6963}\ Shadow Copy Storage volume: (C:)\\?\Volume{3ce0cbe2-57c2-11db-a712-806e6f6e6963}\
Used Shadow Copy Storage space: 1.335 GB
Allocated Shadow Copy Storage space: 1.539 GB
Maximum Shadow Copy Storage space: 4.395 GB
Shadow Copy Storage association
For volume: (V:)\\?\Volume{3ce0cbe3-57c2-11db-a712-806e6f6e6963}\ Shadow Copy Storage volume: (V:)\\?\Volume{3ce0cbe3-57c2-11db-a712-806e6f6e6963}\
Used Shadow Copy Storage space: 12.643 GB
Allocated Shadow Copy Storage space: 13.116 GB
Maximum Shadow Copy Storage space: 14.649 GB
For volume: (D:)\\?\Volume{191fc6ee-5a69-4a34-bb81-80b7b46bba04}\ Shadow Copy Storage volume: (D:)\\?\Volume{191fc6ee-5a69-4a34-bb81-80b7b46bba04}\
Used Shadow Copy Storage space: 500.266 MB
Allocated Shadow Copy Storage space: 1.074 GB
Maximum Shadow Copy Storage space: 14.648 GB
Before I go over each of these, here’s something to keep in mind: the determination of shadow storage size is made when the first shadow copy is created (typically when System Restore is enabled and creates a restore point during Setup) and is set to the minimum of 30% of free space or 15% of the volume. When System Restore is turned on right after Windows Vista is installed, the shadow copy storage area is most likely to be 15% of volume. In cases where System Restore is turned on much later, the 30% of free space formula might kick in, thus limiting the number of shadow copies you’ll have on your system. Also, these percentages don’t increase or decrease dynamically when more (or less) free space is available or after you adjust the size of the volume.
Here’s a quick analysis of these results:
It’s easy enough to decrease the shadow copy storage area, but doing could potentially delete older shadow copies. If you need the free space more than you need a long history of shadow copies, you can decrease the storage area size.
Let’s say I decide to decrease the storage space on my D volume to 10 GB. I would use the vssadmin resize shadowstorage command as follows:
V:\Windows\system32>vssadmin resize shadowstorage /on=D: /For=D: /MaxSize=10GB
Successfully resized the shadow copy storage association
If I re-run the vssadmin list shadowstorage command, I now have the following stats for D:
For volume: (D:)\\?\Volume{191fc6ee-5a69-4a34-bb81-80b7b46bba04}\
Shadow Copy Storage volume: (D:)\\?\Volume{191fc6ee-5a69-4a34-bb81-80b7b46bba04}\
Maximum Shadow Copy Storage space: 10 GB
Next, let’s take a look at how many shadow copies I have. Typing vssadmin list shadows, I get the following condensed output:
Provider: 'Microsoft Software Shadow Copy provider 1.0'
Type: ClientAccessibleWriters
Attributes: Persistent, Client-accessible, No auto release, Differential, Auto recovered
Contents of shadow copy set ID: {b77797ad-2bef-4438-b843-8817eb76cf5d}
Contained 2 shadow copies at creation time: 10/13/2006 5:00:21 PM
Shadow Copy ID: {e68baeda-603a-42e2-b88c-1384e28fa6df}
Original Volume: (C:)\\?\Volume{3ce0cbe2-57c2-11db-a712-806e6f6e6963}\
Shadow Copy Volume: \\?\GLOBALROOT\Device\HarddiskVolumeShadowCopy25
Originating Machine: Jill-PC.contoso.com
Service Machine: Jill-PC.contoso.com
Shadow Copy ID: {9071c059-8ac4-4a3d-983f-1e66ec7a530a}
Original Volume: (V:)\\?\Volume{3ce0cbe3-57c2-11db-a712-806e6f6e6963}\
Shadow Copy Volume: \\?\GLOBALROOT\Device\HarddiskVolumeShadowCopy26
<snipped 12+ similar entries because they are very long!>
Contents of shadow copy set ID: {44a4a066-7ac2-4161-9537-dba9b6025a23}
Contained 1 shadow copies at creation time: 10/20/2006 3:28:20 PM
Shadow Copy ID: {449ce530-cf45-4f58-abcf-9c722dc56cec}
Original Volume: (D:)\\?\Volume{191fc6ee-5a69-4a34-bb81-80b7b46bba04}\
Shadow Copy Volume: \\?\GLOBALROOT\Device\HarddiskVolumeShadowCopy44
Type: DataVolumeRollback
Attributes: Persistent, No auto release, No writers, Differential
A couple interesting things to note about the above output:
For those interested in Complete PC Backup, we are planning a “Power Users Guide to Complete PC Backup” for a later blog post. We’ll talk about sizing recommendations for shadow storage, scheduling Complete PC Backups (using the command-line tool Wbadmin), and more. Should be a good read!
--Jill (with much input from Eduardo Laureano, Ivan Pashov, Jim Benton, Dinesh Haridas, and Dan Stevenson)