Shadow Copies on Windows Server (2008R2)

[seepy83]

I'm looking for some details on Shadow Copies for a 2k8 file server...more specifically some help with capacity planning. This is the first time turning on Shadow Copies in our environment.

We have a volume that has 400 GB of shared folders and My Documents redirected to it. We turned on shadow copies, and set it to store the shadow copy data on another volume that will only be used for shadow copy storage. Since i couldn't find any documentation related to capacity planning, I provisioned 50 GB on the volume used for shadow copy storage (It's a LUN on our SAN, so I can add more capacity very easily) to start.

The first shadow copy took up about 4 GB of space. I waited about 1 hour, and created another shadow copy. The 2nd copy took up 8 GB of space (at this point, 2 shadow copies existed, and a total of 12 GB of disk space was consumed). I then waited overnight for it to create the next shadow copy at 7 AM the next day. The shadow copy volume now has 34 GB of space consumed, and only 1 shadow copy (from 7 AM) available.

The space consumed by the shadow copy/copies is increasing at a very high rate. Is it normal for the size to increase that much? Does anyone know of a capacity planning guide for shadow copies?

 

[corkyg]

The VSS system which started in Vista, and is now in Win 7 is part of the System Restore. And, it can be controlled. In my server, I have all of that turned off because I use duplicate drives instead.

http://blog.szynalski.com/2009/11/23/volume-shadow-copy-system-restore/

http://www.pcmag.com/article2/0,2817,2342534,00.asp

 

[seepy83]

The VSS system which started in Vista, and is now in Win 7 is part of the System Restore. And, it can be controlled. In my server, I have all of that turned off because I use duplicate drives instead.

http://blog.szynalski.com/2009/11/23/volume-shadow-copy-system-restore/

http://www.pcmag.com/article2/0,2817,2342534,00.asp

I don't see how duplicate drives is a replacement for Shadow Copies. Our goal is to make files restores easier when a user calls and says they accidentally deleted something or overwrote it with a new file, etc. We don't want to waste time restoring from the tape backup from the previous night anymore.

I'm looking for some kind of capacity planning guide for it because the disk consumption that I'm seeing doesn't seem efficient. The blog post you linked to said that 5% of disk space is usually enough to store several snapshots of a disk. My first shadown copy was 1% of the size of the data being shadowed, 2nd was 2%, and 3rd was 8.5%. It doesn't seem normal to me that the shadow copy would increase at that rate, because I don't believe data on the volume that's being shadowed is changing that much or frequently.

 

[JackMDS]

http://technet.microsoft.com/en-us/library/cc753975.aspx

 

[seepy83]

http://technet.microsoft.com/en-us/library/cc753975.aspx

Been there, done that. Still no kind of capacity planning guide to be found.

 

[Bubbaleone]

See if reading through Shadow Copy Considerations gives you a better perspective of how your configuration of VSS determines its actual disk space requirements.

 

[seepy83]

See if reading through Shadow Copy Considerations gives you a better perspective of how your configuration of VSS determines its actual disk space requirements.

Your configuration determines how much disk space is allocated for VSS to use, and it determines how often snapshots/shadow copies are made. I understand that. However, It doesn't determine how much disk space is required to keep 'X' number of Snapshots/Shadow Copies of a volume that contains 'Y' amount of data.

I've had shadow copies turned on for a couple of days, and right now 2 snapshots of a disk containing about 400 GB of data is taking up 61 GB on the volume that I've allocated to store shadow copy data. Since I know that the data that I am shadow copying doesn't change very frequently, and it isn't growing significantly, it doesn't seem right that I would need this much space for shadow copies. I would need my shadow copy volume to be 76% of the size of the source volume in order to save 10 snapshots/shadow copies (2 per day, for 5 business days before a shadow is overwritten). That's nowhere near as efficient as I've seen it claimed to be. So I wanted a capacity planning guide, or to see what other people's experiences have been like, to see if this actually is the norm.

 

[rasczak]

Seems the only way you're going to get the answer you seek is to try the different configurations and plan based on your own findings. I understand the frustration though.

 

[corkyg]

I don't see how duplicate drives is a replacement for Shadow Copies.

That's easy. With instantly switchable duplicate drives, System Restore is not needed, and therefore VSS is not needed. Cloned duplicates do not require restoration. Just power off, swap drives and reboot.

 

[seepy83]

That's easy. With instantly switchable duplicate drives, System Restore is not needed, and therefore VSS is not needed. Cloned duplicates do not require restoration. Just power off, swap drives and reboot.

What I'm using VSS for has nothing to do with System Restore. It's so that user's can view previous versions of shared folders/files using Shadow Copies. Thanks for trying, but your needs and mine are miles apart.

Seems the only way you're going to get the answer you seek is to try the different configurations and plan based on your own findings. I understand the frustration though.

I agree...it sucks, but it's coming down to just trying it and seeing what happens with disk utilization.