parity 2 disk can somehow replace parity-swap procedure?


rowid_alex

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here the thing:

i have array with parity drive 5TB and data drive 5TB+1.5TB+1.5TB.

a few days ago the 5TB data disk drive failed and I sent it to vendor for RMA.

in the same time i bought two new 8TB drives and want to replace both the failed data drive and the parity drive.

 

i found out

  • i cannot replace the failed data drive with 8TB drive since the new drive 8TB is larger than the current parity drive 5TB.
  • of course i cannot replace the parity drive with the new drive directly since there is no way to rebuild the data

 

unraid suggests to check "parity-swap" procedure so I found it in wiki:

https://wiki.unraid.net/The_parity_swap_procedure

my understanding is that

  • I have to swap the old parity disk to the missing data drive entry, then replace the parity disk with my new drive.
  • then execute a "parity copy" to copy the parity data from the old parity disk (in data disk entry) to the new parity disk (in parity disk entry)
  • once parity data is copied, start the array will rebuild the data in data disk entry.

 

however i archived with a different way by parity 2 disk since i don't have double parity disks:

  • add the pre-cleared 8TB disk to parity 2 entry
  • start array and sync the parity data
  • once parity 2 disk is ready, stop the array and remove the 5TB parity 1 disk in the configuration and start array again, this removes parity 1 disk from the configuration completely
  • stop the array, now I have a parity disk replaced with a larger 8TB disk in parity disk 2 entry.
  • add the new 8TB disk into data disk entry
  • start the array and rebuild the data.

my questions are

  1. if my procedure is recommended?
  2. if any advantage to use parity-swap procedure than my above procedure?

 

thanks!

 

Best Regards,

Alex

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It will work, I would say there's a little more risk involved since you'll do two rebuilds, or to be more correct, one sync and one rebuild, with a degraded array, to be successful both will need all the other disks to not fail, but as long as everything is healthy you should be fine.

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One more small thing. Parity slot 2 is calculated completely differently. Net result is that now your disks must stay assigned to the same slot numbers to keep parity valid. If you at some point decide you don't like parity 1 being empty and parity 2 occupied, you will have to rebuild parity 1, either by adding it, or breaking parity and running unprotected for the duration of the build.

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9 hours ago, johnnie.black said:

It will work, I would say there's a little more risk involved since you'll do two rebuilds, or to be more correct, one sync and one rebuild, with a degraded array, to be successful both will need all the other disks to not fail, but as long as everything is healthy you should be fine.

ok. what you mean is:

for parity-swap it contains:

  • one parity copy from old parity disk to new disk (this only needs the old parity disk healthy, other than all other disks healthy, since the array is offline)
  • one data rebuild afterwards (this requires all disks healthy)

for what I did via parity disk 2 it needs:

  • one parity sync for parity disk 2 (this needs all disks healthy)
  • one data rebuild afterwards (this needs all disks healthy as well).

is my understanding correct?

 

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8 hours ago, jonathanm said:

One more small thing. Parity slot 2 is calculated completely differently. Net result is that now your disks must stay assigned to the same slot numbers to keep parity valid. If you at some point decide you don't like parity 1 being empty and parity 2 occupied, you will have to rebuild parity 1, either by adding it, or breaking parity and running unprotected for the duration of the build.

thanks. may i know what exactly how the algorithm to calculated parity slot 2 is different than slot 1? personally i don't mind if parity disk is in slot 1 or 2, as long as I have one parity disk.

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