array expansion option ... please confirm my understanding here

[harley-c]

Hi all

 

i currently have an array of 12 x 8TB drives, running dual parity. So 10 data drives + 2 parity. I understand parity vs backup and do actually have a full backup of all data on another server also

 

one of my data drives has failed so needs replacing

 

I will be needing to expand soon also and don't have additional bays so will have to start replacing with bigger drives.

 

I understand that the parity drives are the limiting factor on the useable space of any other drive here so needs to be expanded as a priority, but I need to get the array back to a good state first ideally I would guess

 

Will the following work?...

- replace dead drive with new bigger drive (say 18TB for example). It will rebuild, array will go green, but I will only be able to use 8TB of this due to the 8TB parity disks

- replace one of the parity disks with 18TB drive and let it rebuild ... still the other 8TB parity drive as the limiting factor at this point

- replace final parity drive with 18tB drive and let it rebuild .. now have both parity drives + the replaced drive at 18TB

 

At this point will it start to use the full capacity on those 18TB drives automatically? Or will the data drive i replaced still be stuck at using the 8TB that it could use when it was first replaced?

Any further disk replacement after this will just automatically use the full 18TB?

 

I want to make sure i understand this properly and am not wasting my time here or doing things in the wrong order

 

Thanks

[Gragorg]

What you looking to do is use the new 18TB to replace your parity drive and use your exsisting 8TB parity drive to rebuild your bad data drive.  This procedure is called The parity Swap procedure.

Edited June 28, 2023 by Gragorg

[harley-c]

Thanks. Just read through that and there doesn'ty seem to be any mention of dual-parity so I'm not 100% clear that it will work as it is describing

 

Does anyone have any experience of doing this similar to my setup with dual parity?

 

If i do what it says then i'll end up with one large parity drive and one small oneso not sure what that means and what i'll need to do next to get to a final state where everything could use the bigger drives

[Frank1940]

40 minutes ago, harley-c said:

Thanks. Just read through that and there doesn'ty seem to be any mention of dual-parity so I'm not 100% clear that it will work as it is describing

 

Does anyone have any experience of doing this similar to my setup with dual parity?

 

If i do what it says then i'll end up with one large parity drive and one small oneso not sure what that means and what i'll need to do next to get to a final state where everything could use the bigger drives

It has been my understanding that both parity drives need to be as large as the largest data drive.  If you do a Parity Swap for Parity 1, that condition will be met as both of your parity drives will be equal-to-or-smallerlarger) than the largest data drive (8TB). 

 

You should want to evaluate the size that you want for that new parity drive.  Consider how fast your data storage needs are expanding.  Calculate the cost of drives per TB.  Then consider that the next time, you will be probably be looking at purchasing two new drives of the larger size.  (There is no one size fits all situation/answer to this type of questioning.  Every scenario/answer will have have different pros-and-cons...) 

 

(Personal Note:  You are not the only one in this situation.  I am considering expending my Test Bed server to serve as a backup for my Media files.  I am speaking from my attempt to determine the most economic way to do this.)   

Edited June 28, 2023 by Frank1940
Mistake in logic

[itimpi]

1 hour ago, harley-c said:

Thanks. Just read through that and there doesn'ty seem to be any mention of dual-parity so I'm not 100% clear that it will work as it is describing

 

Does anyone have any experience of doing this similar to my setup with dual parity?

 

If i do what it says then i'll end up with one large parity drive and one small oneso not sure what that means and what i'll need to do next to get to a final state where everything could use the bigger drives

The parity swap procedure is identical regardless of whether you have single or dual parity.

 

The important point is that with dual parity both drives have to be upgraded to a larger size before you can use larger drives in the array.   It is not a requirement that the parity drives be the same size, but neither one can be smaller than the largest data drive.

[harley-c]

I ended up dropping back to single parity, and using the spare disk to replace the failed one so that I can get back into a good state quickly

 

I'll now swap that single parity disk out for a larger one, and then add another larger so that i've got my larger parity set, a spare 8TB in case of failure of a data drive, and the ability to expand in the future

 

Thanks guys