One of my unRAID servers is setup with BTRFS file system, is it necessary to setup scrub jobs, say once a month, is it possible?

I wouldn't call it necessary, since in my experience bit rot is extremely rare, a scrub is good to check data if anything goes wrong, like errors on multiple disks during a rebuild, a disk getting disable when writing new files, etc, if real bit rot happened it would be caught in the next parity check, and in that case a scrub on all data disks would identify if the sync errors are the result of data corruption on one of them.

 

Having said that, regular scrubs are another way to make sure everything is running well, but they don't replace the parity checks, as they only scrub the data, not the disks, i.e., if a 8TB disk has 1TB of data, only that TB will be scrubbed.

 

You can schedule scrubs with the user scripts plugin, if you do, make sure you don't schedule too many at once, as they are very CPU intensive, even a quad core Xeon or similar can only handle 4 or 5 disks scrubbed at then same time.

Thanks very much, that was very insightful.