parity check timing advice


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I have a party check scheduled every 3 months. Currently it's been 77 days since the last one. I'm planning a couple major drive operations and am looking for advice on the best time to manually run a check during.

 

I'm replacing a 2tb data drive with a new 8tb hdd. After the rebuild I will run unBalance to empty the new drive. Finally I will convert my data drives to XFS using the mirror method from the wiki.

 

Should I run a parity check before or after the data drive swap? If before is recommended, can I just run that one or should I do another before starting the conversions? I'm planning on disabling Docker and my appdata backups during the conversion to prevent new data being written to the array.

 

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Run and finish Parity check at all of the following times:

 

1. before any server maintenance.

2. after any server maintenance

3. before moving a server

4. after moving a server

 

But its your data and your server so feel free to take whatever risks you're comfortable with.

 

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 1. before any server maintenance.
2. after any server maintenance.
 


I get that. I guess I'm asking how granular do I consider maintenance? I'm inclined to run a check before replacing the drive. but should I then run another after the rebuild and before FS conversion since they're distinct maintenance operations? I'm inclined to lump them together and wait to run a second check until after all the drives are converted. I only ask because the wiki guide stresses a check before conversion and I'm curious if it's risky to consider the one before drive swap/rebuild as valid for that.

I know that everyone has different risk tolerance but I wanted to see if I'm overlooking any risks by doing both a drive swap and FS conversions between checks. In my mind nothing will change in the array between the operations so shouldn't it be ok to consider parity valid at that point and begin with unBalance immediately after the drive rebuild completes?

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Scheduled checks should be noncorrecting


Mine are set to No in the scheduler's "write corrections to parity disk" field. But I'm asking about manual checks in between a drive swap and FS conversion though. Now I'm confused, does the scheduled check's correction setting impact when I should run a manual check?

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If I knew I was going to do a rebuilt running a parity check before it would make sense to increase the chances of catching an error that might compromise the rebuild.

 

1 hour ago, VelcroBP said:

After the rebuild I will run unBalance to empty the new drive.

 

Why? The data will still be on the removed drive. What are you going to do with it?

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Why? The data will still be on the removed drive. What are you going to do with it?


I agree about the need for a check before a drive replacement and rebuild.

unBalance would be after the rebuild. The FS conversion guide on the wiki indicates that the process requires a blank drive, onto which I move the contents from the drive to be converted. It also indicates that I will need to be certain parity is valid during that process.

Does replacing a data drive have an impact on parity or is it maintained during the rebuild? If maintained then I'm inclined to proceed with the FS conversion immediately after the rebuild.

1. parity check
2. replace data drive and rebuild from parity
3. move contents off new drive and scatter to other disks in the array (via unBalance)
4. proceed with "mirror procedure" FS conversion process as detailed in the wiki guide
5. parity check

FS conversion wiki guide I'm referencing:
https://wiki.unraid.net/File_System_Conversion

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23 hours ago, VelcroBP said:

Now I'm confused, does the scheduled check's correction setting impact when I should run a manual check?

Just wanted to make sure you weren't scheduling correcting checks

23 hours ago, VelcroBP said:

Does replacing a data drive have an impact on parity or is it maintained during the rebuild?

Parity and all other disks are read to get the data for the rebuild from the parity calculation. Not only does rebuild not impact parity, but existing parity is critical to rebuild. And there isn't anything that needs to be done to maintain parity during rebuild, unless some write on the array happens, but that has nothing to do with rebuild except that it has to be handled if the rebuilding disk is written to.

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