JorgeB

The false pending sector issue? That's not file system related.

Seems to be a common issue, some/most times it goes way after a couple of power cycles.

Backplane appears to use regular SFF-8087, so you just need a couple of SFF-8087 to SFF8087 cables, or SFF-8643 to SFF-8087 if you go with a SAS3 model.

It's not

Recently one user with the same controller found it overwrote the first few sectors of every disk destroying the data after a firmware update, did you make any?

That's a known issue, user shares always add some overhead, but some users/configs are much more affected than others, direct i/o shouldn't make any difference with recent releases, IMHO best option is still to use disk shares whenever possible.

Googling the p840 looks like it uses double wide SFF-8087, which is uncommon, first time I've seen those, but if you get for example one of the recommended LSI HBAs you just need to need to get a cable that matches the LSI on one end, regular SFF-8087 (SAS2 models) or SFF-8643 (SAS3 models) and whatever you have on your backplane.

Not familiar with that one, but we don't recommend RAID controllers for Unraid, only true HBAs.

If they don't provide a way of doing it using Linux you're limited to Windows.

Just re-assign it.

Enable the syslog server and post that after a crash.

Yes, will also need to re-configure them. Up to you. Yes.

Yes, those cables are for USB 2.0.

This makes it impossible to answer based on the info provided:

Best way to restore (so that you can keep doing the incremental backups) is to send/receive the backup to the destination where you do the original snapshots on that volume, then create a new read/write snapshot to the original data location, this way data is restored and you can then create future snapshots and continue to incrementally send them to the backup destination.