Extend a volume or create a new volume with a new vdev

[MarkS-Indy]

This question is an extension of my previous question regarding extending/expanding a volume.

I currently have 4TBx10 RaidZ2 vdev and volume in a 20 bay server. I will be creating a new 8TBx10 RaidZ2 vdev to fill the empty 10 bays. The question is this (and I know that an answer might be "it depends"): Is it more efficient/better to extend my current volume with this new vdev, or create a new vdev? Is more information required before a reasonable and rational response can be made?

Any help would be appreciated. Thanks.

 

[Vito Reiter]

I would extend the volume with the new vdev. It will put the vdev's in a striped Raid-0 Array which will increase your performance -especially with enterprise drives- and you'll have a way bigger volume.

Key Notes:

• HDD Size Bottlenecks only exist within vdevs, so you're 8TB drives won't be affected by the fact that the other vdev has 4TB drives.
• Although your total HDD failure threshold will be 4 drives, note you can only lose 2 in each vdev, any more than 2 in a single vdev will cause failure of the whole array
• You can still expand the original vdev in the future by replacing each drive one-by-one with bigger drives
• LOOK OVER EVERYTHING prior to expanding the volume and remember these new vdevs are in RAID-0, so there is no margin of error if you accidently set-up a RaidZ1/Mirror/ETC.

So, the best bet is to expand the single volume, otherwise, no one piece of equipment will be able to take advantage of the full 96TB you should be expecting from the newly expanded volume.