Can I Upgrade My 1 Parity Drive Temporarily Using The Unused "Parity 2" Slot?


Pro-289
Go to solution Solved by JonathanM,

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I have a 3TB parity drive and some 3TB and 2TB data drives. I bought a 4TB drive that I now want to upgrade the 3TB parity.

 

I just had some ultra dma crc issues with a few drives after moving around cables. One went disabled during a write I presume. I had a faulty/arcing power supply which I replaced. Changed out all my cables. Put some ferrite beads over my sata cables for the hell of it. I rebuilt that disabled drive and everything on it seems okay without error.

 

I know I could disable the 3TB parity, assign the new 4TB as parity and rebuild it. But during that 12hr rebuild time frame if I have an issue with a data drive then I'm not protected from getting my array out of wack.

 

Seems the easiest way if possible would be to install a new parity drive and have it copy from old to new in offline mode. Pull the old drive and start the array with out any rebuild, then run a parity check for good measure.

 

When you do Dual Parity drives, are both drives exactly the same as each other? So could I add my 4TB as Parity 2 and have it rebuild onto that. Then remove my 1st 3TB parity and drop back down to a 1 parity drive array without rebuilding again?

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8 minutes ago, Pro-289 said:

 

When you do Dual Parity drives, are both drives exactly the same as each other?

No they aren't.  Different algorithm's are used to calculate Parity 1 and Parity 2.

 

This holds true if Parity 2 is installed and Parity 1 isn't.  (For the most in performance you should always use Parity 1 instead of Parity 2 if there's only a single drive as the calculations are faster and easier on it)  But, this performance hit may only be noticed on a synthetic benchmark.  Nothing stops you from assigning parity 2 and having parity 1 empty though.  The system will still happily (well maybe not happily for your wallet) recover from a single drive failure.

 

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10 minutes ago, Pro-289 said:

 

When you do Dual Parity drives, are both drives exactly the same as each other?

Not even close. The drive assigned to slot parity1 is a simple parity sum, the drive assigned to slot parity2 is a complex calculation that includes slot number of the included data drives.

 

13 minutes ago, Pro-289 said:

So could I add my 4TB as Parity 2 and have it rebuild onto that. Then remove my 1st 3TB parity and drop back down to a 1 parity drive array without rebuilding again?

Sure. As long as you leave the disks all in their assigned slots parity2 will remain valid, no need to have a drive in parity1.

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8 minutes ago, JonathanM said:

Not even close. The drive assigned to slot parity1 is a simple parity sum, the drive assigned to slot parity2 is a complex calculation that includes slot number of the included data drives.

 

Sure. As long as you leave the disks all in their assigned slots parity2 will remain valid, no need to have a drive in parity1.

So what happens afterwards when I remove Parity 1? Will I get warnings about the drive missing, which of course I should? How do I then make the array happy to keep using Parity 2 without Parity 1? I've heard of "new config" before, but not sure how that works.

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18 hours ago, JorgeB said:

You don't even need to do a new config, just unassign parity and start the array.

Yup, worked like a champ. Got my 4TB as parity now without risking issues during the 15 hour rebuild.

Maybe when I get another 4TB, I'll set that as Parity 1 then remove Parity 2 for optimum performance.

 

Thanks for the help.

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