Background: I recently added a new 8TB drive as disk5 to my array.  There was no data on it, completely empty.  While reorganizing some stuff last night I unplugged the server and the UPS died within moments (likely a bad battery) cutting power to the server.  When I rebooted the machine disk4 came up disabled and there was some clicking from the server.  Drive is dead.

 

I didn't have a spare drive on hand and so thought I'd shrink disk5 out of the array (since it was empty),  move the drive to the disk4 position and rebuild.  I did the first part of the shrink process, up to clearing disk5.  Now I'm worried that when I setup a new conifg the data currently being emulated from disk4 will be wiped.

 

Does the following seem like a correct course of action:

1. pull the empty drive from the disk5 position;

2. put it into the disk4 position and rebuild; and

3. modify the config so that the disk5 position is empty?

 

Unraid version: 6.11.5

2 parity disks

Edited February 4, 20233 yr by rsbonini

I think you should be OK if I understand you correctly, assuming you proceed correctly from here. But I'm not entirely clear where to start from.

18 minutes ago, rsbonini said:

I did the first part of the shrink process, up to clearing disk5.

Have you cleared disk5 in the array or not?

 

Attach diagnostics to your NEXT post in this thread.

Diagnostics attached.  Thank you for the quick response.

 

I tried to run the clear_an_array_drive script, but I think it bailed or didn't complete because disk5 now shows: "Unmountable: Wrong or no file system".

 

 

 

cygnus-diagnostics-20230203-2050.zip

Edited February 4, 20233 yr by rsbonini

A clear drive is all zeros. The point of clearing a drive in the array is so parity will be updated to be in sync with all those zeros, and then, the disk can be removed because all those zeros have no effect on parity. So the disk could be removed without rebuilding parity.

 

A mountable drive has a filesystem to mount. So of course a clear drive would be unmountable because it has no filesystem.

 

But if you don't know for sure if it was completely cleared, then I think we have to assume that it isn't clear and can't be removed.

 

I never bother with that method to shrink the array and just New Config without the drive and rebuild parity.

 

More about how to proceed after I look at diagnostics.

 

 

Ok, that makes perfect sense.  I think the drive was cleared, but can't be 100% certain. 

Emulated/missing disk4 is mounted, so that's good.

 

Whether disk5 cleared or not, you should be able to start the array with it not assigned since you have dual parity. Then you would have disk4 and disk5 both disabled. Then you could assign that disk as disk4 and rebuild it.

 

After that rebuild completes, it should be OK to just assume disk5 had finished clearing, do New Config without disk5 and with parity valid. Then a parity check would confirm whether or not it had finished clearing, or if parity needs to be rebuilt after all.

Did the first step as you suggested, reassigned the new empty drive as disk4 and rebuilt disk4.  Appears that the rebuild  completed with no issue.

 

The system reports that parity is valid, with the last time it was checked being the same time it completed the rebuild of disk4.  This means that disk5 was properly cleared and I can now do New Config > Unassign disk5 with valid party checked, correct?

Parity valid report doesn't really mean anything except that it thinks it completed the last parity operation.

 

But you can go ahead with the New Config/Trust Parity and just run a parity check after.

Ok, so I did the disk reassignment with parity valid, that went smoothly.  I then ran the parity check without writing corrections to parity.  The check completed this afternoon, reporting 545 errors but also reports "Parity is valid".  Should I run a correcting check?  The other drives weren't involved in any of the drive dying, unfinished clear, data rebuild fiasco so shouldn't they be trusted more? 

 

A parity check was conducted two days prior with 0 errors.

Edited February 7, 20233 yr by rsbonini

8 hours ago, rsbonini said:

Should I run a correcting check? 

yes

8 hours ago, rsbonini said:

The other drives weren't involved in any of the drive dying

And they are probably not the reason parity is out-of-sync

8 hours ago, rsbonini said:

unfinished clear

This is a likely cause.

 

Correcting parity will make everything in sync again by updating parity so it agrees with all assigned disks.