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Volume Shadow Copy and Page Pool memory

Posted on 2009-04-16
Medium Priority
Last Modified: 2013-11-14
Hello Experts

Long story short.

We have a fileserver running Windows 2003 STD. SP2 32 bit.

The file server is hosting 2.5 million files.(1.1 TB data)
The server is set to Create Shadow copys 3 times a day.

Our server is suffering from Kernel memory page pool depletion. This gives us problems with insufficient system resources. That will make the system unable to handle big file transfers and user logons and RDP connections.

This is due to Volume Shadow Copy. As each snapshot we make steals about 2,5 MB of the page pool memory.

This is normal acording to this Technet article:

Scalability Factors for Shadow Copies

That is why we estimate the paged pool memory usage as being between 1 MB and 2 MB per million files.
Qoute end

So this I understand. And i understand the limitations of the 32bit memory system.

But what i would like to know, is there anyway to limit the number of snapshot by count instead of by size?

I know I can set the size of the snapshot area, but it would be better if I could set the count?

say i would only allow 20 snap shots before the system removes the oldest one.

Can this be done?

This would allow me to control the Volume shadow copy service and prevent it for stealing all of the page pool memory.
Question by:poultarp

Expert Comment

ID: 24156077
Hi Poultarp,

I do not have an answer for this but was wondering if you really need 3 shadows per day?  Also, do you have an appropriate antivirus on the server?  I have seen symantec slow the server down while it was doing its shadow copy.  Are you shadowing to a different drive?  Just some thoughts while someone comes up with an answer..


Author Comment

ID: 24156268
Hello adolphus850.

We dont really need 3 shadows per day. But the number of shadows per day is irrelevant in my eyes.

if we get 40 shadows over a week or 40 shadows over a month, does not play a big difference.
The problems is when we reach too many shadows, we will get in trouble with our memory usage in the paged pool area.

The problems is not slow shadow copys, but for the record we use Symantec Endpoint on the server.
We are shadowing to the same drive as the data is on.

But again, the problem is not with creating shadows this works very good, but setting a limit is a problem.

The max size of a shadow copy area is not enough control for us.

Expert Comment

ID: 24504835
hey poultarp:
just to share... we're having the same problem in our environment. 2 snapshots a day and we get maybe 10 snapshots before we starting having issues.  most common one that users' see for us is PST corruptions and the inability to copy/move large files due to lack of resources to perform the operation.  only difference we have is that we're shadowing to a diff volume (everything is SAN based) and we still have the same issue.

any update on your question?
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Expert Comment

ID: 24776355
I have the same issue. After 5-6 days the server starts rejecting connections and restarting the server is the only solution. When the problem starts the vssadmin list writers fails.

Accepted Solution

rickardc earned 1000 total points
ID: 25131350
I'm not aware of how to limit on anything other than the size.

We have the same problem, on servers with large volumes and millions of files.  Has anyone resolved this problem?  We snapshot to a separate (smaller) drive to keep the number of snapshots down, but then I believe we run into this issue when the snapshots are deleted to make room.

"A computer may run out of paged pool memory if the "Shadow Copies for Shared Folders" feature is enabled in Windows Server 2003"  http://support.microsoft.com/kb/927435/en-us

On our larger file servers we've purchased undelete, which is great for deleted files, but isn't as cool as VSS for rolling back modifications to files.


Expert Comment

ID: 25134951
our conversations with Microsoft says the only way to get around the memory problem is to upgrade to 64-bit. apparently 64-bit does not have the same limitations to kernal and non-page pool memory.  of course this isn't an option for us at the moment so our fix is to scale back the number of snapshots and to cap the snapshots to a total of something like 25GB (even though the drive is like 200GB.

Author Closing Comment

ID: 31570878
Problem was memory pool

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