Reinstalling replaced drive?

[Briadin]

So quick question, long explanation:

 

Have Drives 7 & 8 hanging off of a little SI-PEX40057, suddenly the drives are reporting errors and offlining.  The error count on the two drives was identical, but Drive8 had gotten errored once or twice without Drive7...  so I thought maybe Drive8 is going out and system level 'spiking' Drive7 somehow.  (You can see where this is going)

 

I remove Drive8, start a rebuild and it's going fine for an hour or so when the drives go out again.  Take it apart and the SATA card looks discolored/burnt on the underside.  

 

I now have an LSI 9207-8i coming in, but my question is this:

 

Since I removed Drive8, replaced it and started a parity rebuild, is it possible to just put it back in the system?  Drive7/8 are probably both good (which makes sense since they're the newest drives in the system), but didn't know how possible that is due to the replacement.

 

Also when I get the card, second parity drive.  I've learned my pucker-factor lesson.  😄

[trurl]

Maybe diagnostics would help clarify and possibly show other considerations.

 

Go to Tools - Diagnostics and attach the complete Diagnostics ZIP file to your NEXT post in this thread.

[Briadin]

Sure, though it's from a boot with those two drives removed.  I don't like running with drives down, so I've just offlined the system till I get the card in on Tuesday.  Brought it up, downloaded ZIP, offlined it again.

tower-diagnostics-20200822-1537.zip

[trurl]

The main thing I was hoping for more clarity on was your question.

47 minutes ago, Briadin said:

my question is this:

 

Since I removed Drive8, replaced it and started a parity rebuild, is it possible to just put it back in the system?

Did you replace disk8 with a different disk to begin rebuild? Or were you rebuilding to the same disk?

 

What exactly do you mean by "just put it back in the system"?

[Briadin]

Sorry, yes.  I removed Drive8 and replaced it with a new drive.  The new drive is what the parity rebuild was working on when it failed again.  

 

My question is when I get in the LSI card can I just take out the new drive, put the original Drive8 back in the system and re-import it?

[trurl]

32 minutes ago, Briadin said:

My question is when I get in the LSI card can I just take out the new drive, put the original Drive8 back in the system and re-import it?

Not sure what you mean by "re-import". If the original is the same size as the replacement then you should be able to rebuild to the original instead.

[Briadin]

Ok, great.  So can I just put the original Drive8 back in the server and run with it then?  I won't have to do a parity rebuild on it, correct?  

 

Wouldn't make much sense since all of the data is still present on the drive as far as I know, just not sure how unRaid handles the internal pointers with replacing "A" with "B" in the set then replacing "B" with "A" with all of the original data present.

[trurl]

The disk is disabled so it needs to be rebuilt.

 

Unraid disables a disk when a write to it fails. But that write still updates parity, so that write can be recovered from a rebuild. After a disk is disabled, Unraid doesn't use the disk anymore. Instead it emulates the disk using all other disks from the parity calculation. The emulated disk can be read, and it can also be written by updating parity. So any subsequent writes are also in the array and can be recovered.

 

The actual disk itself is out-of-sync with parity. The only other possible course of action would be to New Config and rebuild the parity disk instead. But since the data disk is out-of-sync and missing those writes, it really makes more sense to rebuild it.

[Briadin]

Ok, makes sense.  Was hoping to avoid the rebuild, but that'll work.  Thank you!