This isn't an error or technical issue, more just general question.
We have Windows server 2012 r2 dedupe enabled on all of our file servers. We have Veeam setup using reverse incremental, keeping 14 restore points, running at 7pm nightly.
This has been working well for us for a few years now.
Every once in a while, we get a huge reverse incremental, and we're wondering if the Windows dedupe might be the cause.
For example, the file server that has this issue has 3 drives. 55GB OS drive, 1.8TB shared drive, and 2.5TB shared drive. The main backup file is right around 4TB for this server. Nightly restore points are usually in the 3-60GB range.
This past saturday night, the restore point is 861GB and took 33 hours to complete (normally under 2). We've looked into the antivirus on the server, but it didn't run any scans over the 48 hours leading upto this. We've looked at new/modified files on the server, but can only account for around 30GB of changes. We've had this happen a few times in the past, also seemingly on weekends when almost no one is working. It's only once every few months usually though, not a weekly thing.
Windows dedupe background optimization is set to constantly run in the background every day, all day. Throughput optimization runs nightly from 1am-5am. On Saturday and Sunday, it runs a garbage collection and a scrubbing jobs around 3am.
Looking at those dedupe logs, the garbage collection and scrubbing jobs only took a few minutes to run, so I can't see how they'd be creating so many changed blocks. The timing of it though is suspicious, since the garbage and scrubbing run on weekends, and these large files seem to happen on weekends.
I saw another thread speculating defragging might be causing it, or antivirus, or dedupe. I also saw an old best practices thread that said to use forward incrementals with Veeam if you have dedupe, but this seemed to be talking about deduping the Veeam backup files.
Does anyone else with a similar setup experience this? It's not a problem, but we'd love to know what's causing it.