Is it necessary to run a scheduled scan on my RN314 for Defrag and Scrub?
Volumes are only JBOD and no Snapshots.
If so how often should these be scheduled to run?
Scrub does both a btrfs scrub and a RAID scrub. While the RAID scrub doesn't apply to JBOD, the btrfs scrub does.
None of these are strictly "necessary". While the defrag is the least useful, I do run it.
My own practice (on all my NAS) is to run one maintenance task a month on each volume. On NAS with multiple volumes, I stagger the schedule so only one task is running at a time.
Personally I enable it. It enables BTRFS checksums on the share, which would give you some more information on what files are damaged if the disk starts to fail.
Bit rot protection does slow things down a bit, and I don't believe it's the default. So it's off because you didn't turn it on. Note that turning it on at this point may not have the effect you want, as it will only affect files created after you enabled it.
The various maintenance tasks cannot overlap, at least if you use the GUI to run them. There would be a lot of disk thrashing, and I think doing a defrag (moving sectors of data) would cause issues with a scrub or balance. Note that if a scheduled task comes up while another is ongoing, it appears it's cancelled, not deferred, so make sure you allocate sufficient time between them. That's one reason for the one task a month plan. In my case, I have three NAS and schedule the tasks on different weeks, allocating two weeks for the scrub since it can sometimes take long. That keeps the added heat and noise down to just one NAS at a time.
