Moving Shadow Copy files to new drive in 2003 Server

Posted on 2006-07-19
Last Modified: 2013-11-15
I have enabled shadow copies on one of the drive on our windows 2003 Server that keeps our data. We are planning to purchase a SAN storage device and want to move the files to the SAN. The same 2003 server will be connected to the new SAN. I am assuming that I can enable shadow copy on the SAN because it will be like an external hard drive. right?  More importantly, if I were to copy the files to the SAN, would I loose all the shadow copy information? Also,  I am thinking of replicating the files from the SAN to another server, would the shadow copies be also replicated.

Question by:netcomp
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Accepted Solution

Lee W, MVP earned 300 total points
ID: 17142736
SAN space is seen as local hard disk space so Shadow Copies should work on a SAN.

You cannot move Volume Shadow Copies from one drive to another.  You would need to DISABLE the service, which clears out the existing shadow copies, then change the shadow copy storage drive and reenable them.

Replicating the copies would be dependant upon exactly how you replicate.  If you put the copies on another drive letter (as I would recommend) and do not replicate that drive, then the copies would not be replicated.


Author Comment

ID: 17143571
What if I am replicating to the folder that has shadow copies enabled. Would it creat shadow copies of the files that are being replicated?

How about when backing up? If I need to restore from backup to the same server? I heard that I need to restoer sytem state also if I am restoring from backup and want to have the shadow copies information?

Leew, I know this is abou Shadow copies , but if we get a SAN and we get a SAN switch, can two servers access the same folder at the same time?

Thank you
LVL 95

Expert Comment

by:Lee W, MVP
ID: 17143636
As I understand the technology, when the file is first placed there, no shadow copy is created (it's the first and so far only version).  As soon as an edit occurs to the file and data changes, thats when the copy is created.

So, if you replicate TO a drive with Shadow copy enabled, the initial copy/replication will NOT create copies.  Subsequent "replications" if your replication technology does "all or nothing" type of replication, then I'm not sure how it will behave.  The technology SHOULD look for changes, essentially looking at a checksum which in theory only changes when the file changes, so that SHOULD be ok.

I've never be in a position to test this backup theory.  In practice you should have various backups and should also realize that shadow copies are a temporary thing and they WILL be overwritten over time which you don't necessarily have any specific control over.  Shadow copies are great, but I don't view them as a primary method of backup and though they are kept in the system volume folder, I don't know if a system state backup would back them up.  I would suspect not and frankly, I wouldn't want to do a system state restore unless the server crashed.  And since your data should be on a seperate disk from the OS, if the OS disk crashes, then the data is fine and vice versa.

In most (if not all) circumstances, you CANNOT access a SAN volume from two servers at the same time.  SANs are often clustered and they will have connections to two servers that can use the same volumes, but only one at a time has access to a given volume. If both could write at the same time, you could potentially corrupt (seriously) your data as there is no native locking mechanism to protect you from access or even writing to the same space at the same time.

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Assisted Solution

carl_legere earned 200 total points
ID: 17157802
Shadow copies are not made based on realtime changes.  They are created according to a schedule, look in scheduled tasks you will see a call to: C:\WINDOWS\system32\vssadmin.exe
The defaults are 7am and midnight or somesuch.  The vssadmin creates a new version by comparing a cache of changes and essentially writes the changes out to a file.

I agree with Leew generally with this exception.

My site with 14 geogrpahically diverse locations all using DFS and shadow copies are configured in such a way that one of the DFS targets has 1.0 terrabyte or so free.  shadow copy service is told to use all the space it wants, leaving 5% free or so.  When you want to restore or view shadow copies you have a choice of going to your local server and view the snapshots it has OR go via the WAN to the 'backup server' who has much free space.  It will have more snapshots, an thus more flexibility for user self restores.  

The backup server also uses tradional backup technologies to multiply the redundancy.  Indeed DO NOT trust shadow copy service.

Sorry I can't comment on SAN to two servers feasibility.

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