2010-02-26 01:51 PM
Building new aggregates is all fine and dandy, but what do I do in a case like this:
Aggregate RAID Size 16 with 15x621G disks
We have added a 14TB shelf (1TB disks) and need to expand the aggregate mentioned above. I don't want to use the entire shelf for this aggregate since I have other aggregates that have the similar setup. I would like to know the best scenario for the best performance with the mixed disks???
2010-02-28 02:28 AM
If you have the time it sounds like your best bet would be to use the new disks to create a new aggr and then mirror the original aggr volumes into it. This would get you at least a little extra capacity. Depends on how much extra you need really, but it might solve your problems based on same size disks. If you have only a portion of the volumes on the original aggr that will need to grow then move them off into the new aggr only meaning that there will be plenty of capacity.
Migration would be preferential to mixing disks as this helps with the balance.
The worst case if you must mix is ensure that the new disks go into a second plex, this will mean that the RAID group is balanced even if the whole aggr isn't.
Hope this helps
2010-02-28 11:35 PM
Adding all 1 TB disks to your existing aggregate won't work because of the 16 TB raw maximum aggregate size. Also using a few disks to expand the current aggregates will only result in waste of parity disks, you need to start a new raid group to get the full capacity of the 1 TB disks, and performance problems because you add just a few disks.
Your best choice is to create a seperate aggregate and copy (some) of the data.
2010-03-01 09:42 AM
Thanks guys! I was almost %100 on that ideology! We have a few admin's and one of them has added larger disks to the aggregate. We don't have enough spare disks to do a disk replace. Is there a way to remove the disks from the aggregate without losing data? Will it write to free space within the aggregate on other disks?
2010-03-01 09:53 AM
Unfortunately, once disks are added to an aggregate, the only way to remove them is to create a new aggregate, copy your data over to the new aggregate, destroy and rebuild the old aggregate, and copy your data back.
I've done this a few times for customers as a paid engagement. It's not particularly difficult, just time consuming and often requires a 'loaner' disk shelf to create the new aggregate to temporarily store the data.