As per the title really, I have a disk that is showing read errors, a long SMART test also shows them. Have swapped the cables over with a different drive in the array and the problem follows the disk.

 

Anyway, all my disks are 4TB ones including my two parity drives, so what I'd rather do is pull Parity 2, put that in place of the failing drive and rebuild it. Then pop an 8TB in in place of Parity 2.

 

Would I need to preclear the parity disk again before adding it to the array as a replacement data disk or am I ok to just stop the array, unplug the failing drive and start the array with parity 2 in its place?

If you were going to actually ADD it as a new disk, then it would have to be cleared. Since you are going to use it to REPLACE an existing disk it doesn't have to be clear.

 

Not entirely sure what the steps would be to get it to give up parity2 and let you use it as data though. Might have to go through New Config.

 

Wait for others ( @johnnie.black ) to reply.

You can, you need to stop the array, unassign parity2, start the array, stop again, assign old parity2 as the disk you want to replace, start the array.

And then after it has rebuilt the disk just add the new 8tb in as parity 2? Will it be ok with Parity 1 still being a 4tb, I assume it will be?

 

 

Sounds easy guys, thank you for your help

Edited August 10, 20178 yr by thebaldconvict

9 minutes ago, thebaldconvict said:

Will it be ok with Parity 1 still being a 4tb

 

Yes

I think it slightly humorous that you go to the expense of having a second parity to protect you from a second failure while recovering from an initial failure. But at the exact moment that you have the initial failure you are going to repurpose your second parity and hence lose protection while this rebuild occurs. 

 

Why do you have it if not for this exact situation?

I wont lose protection completely though will I? Actually would I? I would be down a parity disk AND I'd be down a data disk (potentially)....

 

Hmmm, I was originally thinking I would be protected while parity 2 was being rebuilt but since one drive is having read errors I might not be...  I haven't thought this through have I ha ha......

 

 

I could replace this data disk with another 4TB and then replace the parity with the 8TB and then move that parity and add it as a new disk to the array I guess.... Would keep it protected though out the process that way, I definitely want one of the parities to be an 8TB though for upgrading in the future (and I already have it) too LOL

You could also follow the Parity swap procedure which allows you to in one operation replace a parity disk with a (new) larger one and use the old parity disk as the replacement data disk.   This is not an infrequent operation.

 

This operation actually has 2 phases - the first one copies the old parity information to the new parity disk, and then the second one does the rebuild to the old parity disk.  The big advantage is that there is no requirement to have a spare unused drive of the size of the failed data drive.

Edited August 11, 20178 yr by itimpi

That's also am option, it only works with parity1 though.

Forgive me if this is a stupid question but is that not what I was planning to do albeit manually and with parity 2?

 

If there is a better way to do it though I can swap Parity 1 no worries, it is exactly the same type of disk at Parity 2.

https://wiki.lime-technology.com/The_parity_swap_procedure

Oh I get it, yes, perfect!

 

Thanks again all

 

Edit.. Any way to keep the array usable while it rebuilds the Parity, it says in the guide to'll be offline for the duration and thats going to be a long duration on an 8TB.

Edited August 11, 20178 yr by thebaldconvict

1 hour ago, thebaldconvict said:

Oh I get it, yes, perfect!

 

Thanks again all

 

Edit.. Any way to keep the array usable while it rebuilds the Parity, it says in the guide to'll be offline for the duration and thats going to be a long duration on an 8TB.

Parity cannot be allowed to change while it is being copied because the copy wouldn't be correct. I've never done a parity swap so I don't know if it lets you use the array again after the copy phase has completed or not.

I just have to say that this parity swap process is somewhat infrequently used. And I have not seen it done in a dual parity model. But does seem like the right trick for this situation.

It works with dual parity (with parity1 only), the array will only be available during the disk rebuild, after the parity copy.

Hi all, back again just to give feedback on what I ended up doing.

 

So I didn't want the array offline for ages (and it would have been), it is school holidays and the Mrs (and 5 kids) would have murdered me for Plex been offline and it has a Pi Hole VM also so internet would have been down too soooo I replaced the 4TB.

 

So basically I bought a 4TB to go alongside the 8TB that I wanted to swap in rather than risk the array. I replaced the 4TB with the new drive and rebuilt using the standard process keeping dual parity throughout, then when that had finished I shutdown and pulled the 4TB parity 2 disk replacing it with the new 8TB and set it off doing a rebuild. Well now a parity rebuild takes 21hours so at a guess if I had done a parity swap my array would have been offline for 21 hours?

 

Anyway, the array remained available throughout and at all times I had a protected array.

 

 

Thank you all for your advice, it cost a touch more but now I am left with a tried and tested spare data disk (The original Parity 2 disk) and was protected all the way. AND I'm halfway to being able to use 8TB disks too

 

 

Cheers

 

Tim

5 hours ago, thebaldconvict said:

I bought a 4TB to go alongside the 8TB that I wanted to swap in rather than risk the array.

 

@thebaldconvict Dude you might the right decision!!!  IMHO don't risk nothing! I totally would trust anyone who's already commented in this thread, their all experts and I'm sure their 100% right. But all the variables introduced that you can't control, things can go wrong in the most unexpected ways.

 

Sometimes things don't go as expected. $hit goes sideways. Avoiding the potential for pain by spending $ on a drive you didn't plan on buying sucks but vs. the little pleasure gained by saving $ on not having to buy a drive... I learned the hard way many times before I wised up. A+ job sir.