Disk Upgrade - Can I Stop Upgrade and Replace With Original Disk With No Parity Issues?


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help please: my new to me Supermicro 36 bay chassis was running fine for a number of days; decided to upgrade the size of a disk; did the normal disk upgrade process:

 

1. stop array

2. unnassigne smaller disk

3 assign larger disk to same slot

4 start array

 

(note: all dockers/vms off.)

 

disk upgrade/rebuild started. everything seemed fine. then during the first hour a few UDMA CRC errors appeared on 6 disks that are in the rear backplane.  prior to this there were no disk connection issues.  so, i acknowleged the errors and watched if more would appear. got a few more on each of the same 6 drives. so, i paused the rebuild. powered down. and checked hardware to find the problem.

 

my understanding with UDMA CRC Error Count errors is they are an indication that a physical connection between the drives and host is compromised in some way, often being bad cables or poor connections.

 

i think the issue is with the one SFF-8087 to SFF-8087 cable that connects the rear backplane to the sas hba.  it two spots on its length that are suspect, especially when compared to the other cable.  the other cable connects the same sas hba to the front backplane, with no problems there.  the connectors on the backplanes and sas hba all appear fine and are tight.

 

(note: no dockers/vms were run at all during this process.)

 

(2nd note: i have a replacement cable ordered, plus a couple extras for spares.  but i would like to run the array in the meantime.  and the normal reading of the array disks did not induce UDMA CRC errors.)

 

 

Q: can i just unassign the new disk and replace the old disk and not have parity issues?

 

 

thank you in advance.

 

Edited by DoItMyselfToo
fixed typo
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i reseated the rear backplane connector, in both the backplane and hba then double checked all other connections.  it's been nearly 7 hours since the rebuild started and so far so good.  i am still interested to learn the answer to my original question if anyone knows more about parity syncing/rebuilding.

 

thanks in advance.

 

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15 hours ago, DoItMyselfToo said:

Q: can i just unassign the new disk and replace the old disk and not have parity issues?

You can, you'd need to do a new config, but for parity to still be 100% in sync with the old disk the rebuild would need to be done in maintenance mode.

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No, procedure needs a new config using the "parity is already valid" option before array start, but like mentioned parity would only be 100% valid if the replacement was done in maintenance mode.

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4 hours ago, JorgeB said:

You can, you'd need to do a new config, but for parity to still be 100% in sync with the old disk the rebuild would need to be done in maintenance mode.

so to do this looks like one would have to stop the array, remove the new disk. and replace with the old disk.  and then use the "recipe" from Unraid 6/Storage Management to reset the array configuration in maintenance mode.  anything else?

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Posted (edited)

thank you.  this makes sense.  i seem to have tracked my problem down and the disk rebuild seems to be fine, though knowing more about this can only help in future.  one "bad" thing about Unraid is that it works so well that when it doesn't i cannot remember how to fix anything.  lol.

Edited by DoItMyselfToo
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