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Read Errors While Rebuilding to Upgrade a Disk

Featured Replies

  • Community Expert

Format is a write operation. It writes an empty filesystem to the disk. When you perform this write operation to a disk in the parity array, parity is updated so it is in sync with the empty filesystem just written. So, rebuild can only result in the empty filesystem.

 

So now if a disk dies, I have no way to rebuild? 

  • Community Expert
13 minutes ago, nico44 said:

So now if a disk dies, I have no way to rebuild? 

Don't know where you got that idea.

 

If you format a disk that is disabled and being emulated by the parity array, then rebuild will result in a formatted disk.

 

 

Just new to all this stuff. Is there a way to fix this or it will need a complete set up? 

  • Community Expert

I don't understand what your situation is currently.

 

Attach diagnostics to your NEXT post in this thread.

  • Community Expert

If I understood correctly disk5 is new, it dint 't have any data correct? In the logs it shows it was recently formatted and it's now mounting, so all looks good.

Old disk 5 that died had data, New disk 5 that has been installed and formatted.  

  • Community Expert

Since you formatted new disk5 in the array, parity agrees with new disk5 empty.

 

If you can't get any data off old disk5 or some backup it is gone.

Being this is new to me. Looks like the system runs in raid 5, because I was trying to upgrade disk 1 with a bigger drive I had disk 5 fail. I put back disk 1 and it repaired missing files. When I replaced disk 5 with new disk I have formatted it. Does this mean that it is no longer raid 5 and that disk 5 is separate for the array?  Or I'm safe from anther drive failure? 

  • Community Expert

Unraid is NOT a traditional RAID. Each disk in the array is an independent filesystem that can be read all by itself on any Linux. There is no striping. The parity disk is separate from this and contains none of your data, it just contains parity bits that allows the contents of a missing disk to be calculated from the contents of all the other disks.

 

https://docs.unraid.net/unraid-os/manual/what-is-unraid/#parity-protected-array

 

Disk5 is part of the array, but since you formatted it in the array, parity is in sync with that newly formatted disk. So, there is no way to recover the previous files from the parity calculation, since parity agrees the disk is empty.

 

You are safe from another drive failure, but if you make the mistake of formatting a replacement in the array, it will be an empty disk.

 

You must never format a disk in the array that has data you want to keep. Even if the disk is disabled. Parity emulates a disabled disk, and rebuild will rebuild the emulated disk.

 

The correct approach to an unmountable filesystem is to repair the filesystem as explained at check filesystem. If the disk is disabled and unmountable, preferably you would repair the filesystem on the emulated disk before rebuilding, since rebuild will result in whatever contents the emulated disk has.

 

Was going through the files and I see everything is there. The only thing I see on the array is that disk 1 and disk 2 has more gb used and disk 5 has only 27.9gb. Looks like that the old data from disk 5 went on disk 1 and 2 when disk 5 was formatted. 

 

Should I do a parity check every week? and add a second parity disk for the extra protection. This would give me the safety of 2 drive failures (including parity drives) ?

 

Thank you for the clarification 

Screenshot 2023-12-30 133502.png

4 minutes ago, nico44 said:

Looks like that the old data from disk 5 went on disk 1 and 2 when disk 5 was formatted. 

The system will never do that for you.

 

4 minutes ago, nico44 said:

Should I do a parity check every week? and add a second parity disk for the extra protection. This would give me the safety of 2 drive failures (including parity drives) ?

Monthly suffices.

 

Single or dual parity drives are entirely up to you and your own level of confidence.

 

Actual drive failures are exceedingly rare.  And additionally, a URE does not constitute a drive failure in Unraid (rightfully so) unlike a traditional RAID system.  

  • Community Expert
35 minutes ago, nico44 said:

The only thing I see on the array is that disk 1 and disk 2 has more gb used and disk 5 has only 27.9gb. Looks like that the old data from disk 5 went on disk 1 and 2 when disk 5 was formatted. 

You must have written more to disk1 and disk2 than you remember. And if you aren't missing files that were on disk5 before you formatted it, then disk5 must not have had any files on it before.

13 minutes ago, trurl said:

You must have written more to disk1 and disk2 than you remember. And if you aren't missing files that were on disk5 before you formatted it, then disk5 must not have had any files on it before.

I'm 100% sure that disk 5 went on disk 1 and 2. Disk 5 had about 400 gb before. 

 

How do I know that the array are working properly ?

 

Thanks for all the help 

 

  • Community Expert
1 hour ago, nico44 said:

I'm 100% sure that disk 5 went on disk 1 and 2. Disk 5 had about 400 gb before. 

I'm 100% sure that nothing built-in to Unraid would have done that. We have been using Unraid for more than 10 years and have 10s of thousands of posts on this forum helping people. And lots of other people with a lot of experience would certainly agree that it just doesn't work like that.

I don't know then, but I do have all my data. 

How can I check to see if the array is working correctly ?

  • Community Expert

Do you have Notifications setup to alert you by email or other agent as soon as a problem is detected?

 

You should install Fix Common Problems plugin.

 

Are there any SMART warnings 👎 for any of your disks on the Dashboard page?

 

A parity check would exercise all of your array disks and their connections.

43 minutes ago, trurl said:

Do you have Notifications setup to alert you by email or other agent as soon as a problem is detected?

 

You should install Fix Common Problems plugin.

 

Are there any SMART warnings 👎 for any of your disks on the Dashboard page?

 

A parity check would exercise all of your array disks and their connections.

 

I will set it up

 

Just installed Fix Common problems - Macvlan and Bridging has been found . In Red

 

Nothing on the SMART warnings from the Dashboard page

 

Parity check will be done soon

 

 

 

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