DFS backup and performance issues
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Written by Mitch Ross, on 05-03-2007 16:25

Servers running DFS and Windows 2003 R2 experience very slow backups, and sometimes no backups at all.

Applies to BE10Applies to BE11

Symantec changed how they select and backup files on servers running DFS (DFSR), on Windows 2003 R2. Previously, files could be selected just as any other file.

Starting with 10d Hotfix 29 & 31 (both of which are included in SP2), and all levels of 11d, Backup Exec requires the use of the "DFSR Writer" when backing up and restoring folders used by DFS.

Implications of this are:

  • Files replicated by DFS can on longer be directly backed up (i.e. D:\DSFRoot\Data\*.*)
  • Attempts to do so fail without an error message or warning. Jobs show a byte count of a few Kb of overhead, but 0 bytes of data.
  • The new "proper" way to select DFS replicated is convoluted and not obvious. Folders are buried 4 levels under "Shadow Copy Components", even if you don't run Shadow Copy on that server. See http://seer.entsupport.symantec.com/docs/281856.htm
  • The new method results in drastic performance drops (Between 40% - 90% slower in tests). On one of our production servers, a nightly backup job went from 5 hours to over 22 hours.
  • Backup performance with new method is highly impacted by users accessing the server.
  • Backups from the new method now cannot be redirected when restoring
  • Depending on your post-31 hotfix level, the new selections may disappear and all DFS backups fail after the first backup. See http://seer.entsupport.symantec.com/docs/284186.htm

Workarounds

  • Don't upgrade to SP2, Hotfix 29, Hotfix 31, or 11d.
  • Stop the "DFS Replication" service when backups are running, using pre & post commands

Misc Comments:

Many calls to Symantec support (after trying to connect for about 8 business days...) finally led to the comment that "we have to do it this way", and "using the DSFR writer is much, much slower", with the only reasoning being that Microsoft said so. See also http://seer.entsupport.symantec.com/docs/281856.htm

There are no notes from Symantec about the implications of not using Hotfixes 29 & 31 on a DFSR server, nor the implications of backups run with a stopped "DFS Replication" service.

Associated Articles

There is a real-world hint at Backing up DFS data.

Last update : 03-07-2007 11:03

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1. 29-05-2008 23:59

fake title
well, we were backing up the drive instead of using shadow copy components distributed file system replication backup.  
 
Files went missing, went to backup, all I get is a "DfsrPrivate" folder, holding "ConflictAndDeleted" and "Staging" so I'd say this is current. 
 
I've placed a support call and am waiting for a response.
Guest
mike

2. 16-04-2008 21:40

Screwed
I just knew backup exec would go to hell when symantec bought it. And here it is :)
Guest
Freaky

3. 08-04-2008 04:31

BE12
Is this comment for BackupExec 12? :?
Guest
BE12

4. 03-04-2008 19:30

Slow Backup of DFS Shares
After hours of testing I found out why my DFS Share of 260gig was taking on average 32 hrs to back up! 
 
It was a combination of the following: 
P. = Problem 
A. = Answer 
R. = Result 
 
P. SP1 has issues with DFS and Backup Exec  
A. Upgraded to SP2 and Hotfix 31 
R. 260 Gig in 23hours 
 
P. DFSR Still slowing down Backup 
A. Stop DFS Services with PRE and POST commands 
R. 260 Gig in 14hours 
 
P. Antivirus software was scanning on access. 
A. Changed to scan on Modify 
R. 260 Gig in 7 hours 
 
P. Disk Defragmented  
A. Defragmented the volume 
R. 260 Gig in 5 hours 
 
Good Luck
Guest
Jerry

5. 24-01-2008 04:54

...
Is this knowledge current or deprecated?
Guest
timtrace

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