Non-Exclusive VSS Exchange Backups
Posted on 2011-04-24
I am running an Exchange-aware backup program (SonicWall CDP Version 6.0) that uses the MS VSS writer and truncates the Exchange log files. Full Exchange backups are run every couple of hours and finish quickly with little disk space usage due to deduplication. I also run an image backup solution (Acronis Version 10) that uses Volume Snapshotting but does not truncate the logs or use Application Snapshotting. I had intended to always turn off all VSS capability in the Acronis but have inadvertantly run some image backups that snapshot the volume containing the Exchange database. My concern is whether snapshots from the image backup software might potentially confuse the primary Exchange backup software. Given that the Acronis does not take application snapshots, should my Exchange backups still be ok? It is a long and painful procedure to reseed the Exchange backup so I'd like to avoid doing so if it is not necessary.
On that subject, can someone verify explain how VSS backups work in Exchange? Does the backup compare the current state of the EDB and log files against what is already backed up on backup media? Or does the system remember the state of the last snapshot and only record what has changed since that point irrespective of what is on the backup media? Is it safer to always take full image backups of the volume containing the Exchange Store rather than incrementals/differentials? Or does this vary entirely depending on the backup program? I have customers using Acronis, Backup Exec System Recovery (which is Exchange-aware) and the SonicWall CDP.
Also, can anyone suggest any easier method to validate an Exchange backup set than what I use? To be safe I restore the entire EDB file and all log files to disk and then run ESEUTIL against these files. This can take hours which is a deterrent to frequent integrity checks.
If I am asking too many questions in this one post then please let me know so that I can break up this question in order to reward points appropriately.