Parity rebuild: Did I do a dumb?


craigr

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I think I am OK, but since all my data could be at risk, I want to make extra sure.

 

I replaced both the parity drives in my machine migrating from 8TB to 14TB.  During the parity rebuild I needed to write data to the array.  I have COVID and my brain is far from 100%.  I paused the parity rebuild while I wrote the data to the array thinking it would be faster as with a new array and no parity.  Of course, this was not correct because while writing the data to the array all hard drives in the array including the new parity drives were actively being written to.  Along with the fact that I have confidence unRAID would be "smart" enough to deal with this, the fact that all discs active tells me my parity is sound.

 

Am I OK or is it prudent to resync parity again (sigh) when it finally finishes?  I am trading out 12 more drives and don't want to rewrite them with corrupt parity data and basically lose everything!

 

Thanks for confirmation (hopefully),

craigr

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1 minute ago, craigr said:

I paused the parity rebuild while I wrote the data to the array thinking it would be faster as with a new array and no parity.

It is faster since the disks don't need to do 2 things at the same time. Pausing is not a problem, what's already been built is kept valid and what's not will be done when you resume.

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Also worth noting, I am doing two drives at a time with dual parity.  Before beginning each dual drive swap, I am backing up my flash drive so that if a drive fails during rebuild, I may revert to the prior config and replace the new drives back with their old drives which still contain valid data.  This way I am staying safe even if I lose a drive.  I realize it's not the absolute best, but it's pretty sound and I have 14x 14 TB drives to swap so it's a huge time saver.

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10 minutes ago, Kilrah said:

It is faster since the disks don't need to do 2 things at the same time. Pausing is not a problem, what's already been built is kept valid and what's not will be done when you resume.

That was my reasoning, but in this case since I already had had parity it was not faster.  The parity (all though not completely rebuilt yet and with rebuild paused) and all other drives were still written to when the data was transfered to the array.  Logic would dictate I am safe I think...  I just want to be absolutely certain.

Edited by craigr
(all though not completely rebuilt yet)
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29 minutes ago, craigr said:

Also worth noting, I am doing two drives at a time with dual parity.

 

27 minutes ago, craigr said:

Logic would dictate I am safe I think...  I just want to be absolutely certain.

If you want to be safe you do it as recommended and only one drive at a time. 

Swapping 2 at a time if a drive that hasn't been swapped yet dies during the process you'll lose what's on it. 

 

 

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24 minutes ago, Kilrah said:

 

If you want to be safe you do it as recommended and only one drive at a time. 

Swapping 2 at a time if a drive that hasn't been swapped yet dies during the process you'll lose what's on it. 

 

 

Not if I restore my flash to its prior config and replace the original previous two drives.  I can't lose any data because the data is still on the original discs and can be used to rebuild a bad disc if that happens.

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