Sanapshots and RAID redundancy are two entirely different things, and RAID5 (as you get with 3 drives and XRAID) doesn't have a deicated drive fore redundancy.
But nontheless, it does appear that there is something wrong with your drive 3. It should not be showing as "unknown". I suggest you power down the NAS and test drive 3 in a PC using manufacturers tool (or SeaTools works pretty well on just about any drive). You should probably check the others, too, just in case.
If a drive comes up bad, then you know it needs replacement. But that would usually come up as "dead" in the GUI, not "unknown". The best way to replace the drive is to boot with just the two good drives and add the new one with power applied.
If all drives check out OK, then try booting with just drives 1 & 2. I expect that will work, since drive 3 seems to be the problem. Once you are up and running, re-insert drive 3. You may need to go to the Volume page and format it. Hopefully, it will then re-sync with the volume.
If booting with just drives 1 & 2 doesn't work, then try other combinations of two.
Note that the re-sync puts a stress on the drives, and the chance of a failure of another drive during the process is higher than normal operation. So, it's good you say you have a backup.
Thanks for the quick reply and actions. Just a quick question before I start. Should I eject the backup drives from the system before beginning the troubleshooting, or just disable the backup tasks? I may just obtain a new disc and replace the 3rd drive before troubleshooting it. If it is hosed, then I already have the replacement. If is tests out OK, then I have a spare. Another question is what log files(s) whould I be reviewing to check on the issue? The log file for the last SMART test is old (last test 12/18/2016). Are there others that may yield a clue?
The log file for the last SMART test is old (last test 12/18/2016). Are there others that may yield a clue?
Look in disk_info.log - it should also have SMART status. mdstat.log can be confusing, but it's not to hard to confirm which drive is not in the array.
I suggest rebooting the NAS first and see if the status changes.
If the status is still unknown or good, then you can run the disk test built into the system (volume tab, click on the settings wheel). This will test all the disks. That would be an alternative to testing the drives in a PC.
I may just obtain a new disc and replace the 3rd drive before troubleshooting it. If it is hosed, then I already have the replacement. If is tests out OK, then I have a spare.
The most important thing is to make sure you have an up to date backup.
Having a drive on hand is a reasonable idea. If you can test it in a Windows PC (Seatools for Seagate, Lifeguard for Western Digital), then I suggest doing that.
After a reboot, disc #3 status changed to RESYNC. Guess I will know in 48 hours if all is well, then I can run the disc test from the system interface. Keeping fingers crossed!
After a reboot, disc #3 status changed to RESYNC. Guess I will know in 48 hours if all is well, then I can run the disc test from the system interface. Keeping fingers crossed!
