Regular slow backups on deduped Windows 2012 server

[trevora]

One of the servers we back up is a file server running 2012 with dedupe enabled. We run a reverse incremental backup Mon - Fri which on Tue - Fri takes around 90 mins to complete, transferring around 25 Gb during that time (total disk size is 1.8 Tb). However, on every Monday night the backup can take 24 hours or more to complete, transferring 400+ Gb. Other servers within the same backup job take the normal amount of time to backup so it's definitely VM related rather than a hardware\Veeam issue. My initial thoughts about the cause of this was that the backup is including changes from Sat, Sun and Mon , rather than just the previous days changes (as happens Tue - Fri). However, our company does not really operate at weekends and there is definitely not that much occurring on the server to explain this difference.

I've had the following thought though, and was wondering if anybody had any experience on this. Our server is set to dedupe files that haven't changed for 5 days. Is it possible that the extra couple of days at the weekend means more files reach that 5 day cut off and the dedupe function in Windows ends up changing large areas of this disk thus meaning the next rev. incremental backup is much larger than you would otherwise expect?

Please could anyone let me know if this is a possibility or if they have any other idea what may be occurring?

EDIT: logged with support on Case # 00676667.

[tsightler]

Most likely it is caused by the weekly Scrubbing and Garbage Collection jobs that I believe by default run on Saturday morning. These jobs reorganize the dedupe pool and thus make huge amounts of changes to the disk.

http://technet.microsoft.com/en-us/libr ... DedupSched

[trevora]

Thanks tsightler - i've just checked our dedupe schedule and it is indeed set to run on Saturday mornings as you've said. I'll do a bit of reading, but I assume there isn't much we can do about this?

[meeyou]

If your company doesn't really operate on weekends you could run a backup of that VM on Saturday night so that the big incremental occurs then instead of on a business day. Won't help you with the additional target disk usage though...

[trevora]

If your company doesn't really operate on weekends you could run a backup of that VM on Saturday night so that the big incremental occurs then instead of on a business day.

Unfortunately we run full backups at the weekend already in a separate job (on a different Veeam server) to the reverse incrementals that we run daily, so there's an issue of the jobs clashing if I try that. I'm currently thinking of moving the dedupe schedule to run on a Friday morning. This would make the Friday night backup the long job and not the Monday night one. All I have to do then is make sure the Friday night backup of the server completes before the Full backup job of that server starts on the Saturday. And then, when I come in on a Monday morning, all the jobs would have completed and the Monday night job should be quick. Simples!