[Disk] There is a hardware error on the slot X disk!

[IPhantom]

AS3204T
ADM 3.1.4.RID1
WD30EFRX

[Disk Doctor] S.M.A.R.T full scanning of Disk 4 result: completed without error.
[Disk Doctor] S.M.A.R.T full scanning of Disk 4 has finished.
[Disk Doctor] S.M.A.R.T full scanning of Disk 4 has started.
[Disk] There is a hardware error on the slot 4 disk!

Error is gone after restart, returns with a few hours run time.
What does that mean?

[orion]

If your disk-4 is single volume without RAID protection, it's possible (but very rare). Re-writing data back to sector can recover it. However it's only a possible case.

[IPhantom]

Thanks!
Currently it is Raid 5 with two of the same type and one 10TB.
The error message is not very descriptive. I wonder what kind of error it is and why SMART is not detecting it.

[Antonios]

It's probably on its way out, not a R/W error that would mean surface defect but something else like some fault on the PCB or whatever.

Better make plans to restructure the array(s) although the existence of the 10TB indicates that you might be doing that already.

Just my 2c.

[IPhantom]

I found another message in the Storage Manager: Overview. The disk has a red X (not a blue tick) saying "Deployment: Volume 1 (Media Error).
Under Storage Manager: Disk there is a blue tick and everything normal though. What the hell?

[Antonios]

Mate, just get another HDD to put in there, say borrow one for a few days and rebuild on that, see what happens.

It's either the HDD itself or the host circuit in the NAS, take your pick but without substituting the HDD even for a short period just for testing purposes there is no way to tell.

Assuming that the fault lies with the HDD, it could get worse or it could remain like that indefinitely, in the latter case a less serious task could be assigned to that HDD like secondary external backup in an enclosure or something, but I would remove that HDD from the NAS asap.

Just my 2c.

[IPhantom]

Your suggestion to remove it asap, is it based on data loss prevention or something that might spread or affect the whole system?
Thanks!

[Antonios]

Well, it is what I would do, that's all.

I just wouldn't want a faulty part inside a mission critical system because I wouldn't know what it would do next.

R/W faults are about data loss, not a very serious concern by design in a RAID system but hardware faults might affect the host system depending on how the fault develops over time and that is very serious in my book.

Just my 2c.

[orion]

mm... If it's media error, it's highly possible to be a disk error. You can swap disk 3 and disk 4 after NAS is off. Then turn NAS on. Leave NAS working for a while. If disk 3 got error, it should mean disk error, rather than NAS hardware slot error.

[IPhantom]

Say i would put the faulty disk to another slot, would the NAS recognize the disk by serial number or something so that it is clear it was already in the RAID or would it want to migrate it?