How to grow a hardware Raid 5?

Question

I have a Dell PowerEdge 2970. Currently it runs as a ESXi server with a handful of VM's on it. I have 3 300GB drives plugged in to it, and 5 open trays across the front. It is setup as a hardware Raid5 from the factory. My question is if I start running low on disc space, can I just add on by pushing another hard drive into a empty slot, or will I need to back everything up and rebuild the array? If I can't just plug in another hard drive, would it be better to add 3 more drives, and build a second Raid5 to avoid losing any data that I have

Solution 1

I couldn't disagree with joeqwerty more to be honest. You don't mention which controller you have but all of the PERC 5 and 6 cards can perform live array expansion, although I'd be strongly tempted to fully backup your volume first. This way your new drive/s will become part of the R5 array and so will be able to survive a single disk failure. If you simply add another extent then in the event of losing a disk you stand a good chance of losing the whole VMFS datastore (the risk lessening if you're on ESX/i v4), plus expanding the array to 6 drives gives you 300GB more space than two 3 drive arrays.

Solution 2

The simplest thing to do might be to create a new RAID5 array and add it to the VM datastore as a new extent.

Comments

[Admin]

did some hunting around. I have 3 300GB 10,000RPM drives. The controller is a PERC 6/i Integrated.

[user1364702]

If your storage needs hold out long enough to get a whole new server, that's what I'd do instead, but if you get squeezed then the "safe" route is probably adding a new datastore. Some controllers will let you "grow" the volume, others not, others are supposed to allow it but there's a chance something will go kerplooey so you'd end up backing up and restoring anyway (especially with RAID 5 issues and unrecoverable disk errors...BIG issue now...we were bitten by it on a dell server with RAID 5)

[joeqwerty]

Ouch. Good points. My way is one way, but may not be the best way (but it probably is the simplest).

[Chopper3]

to be honest I've only ever live expanded HP controllers, which I trust a lot more than PERCs, but they have worked each time - even though I was very nervous

[Ruben]

It's worth noting that not all RAID cards can do live expansion. I spent quite some time talking to LSI, and the rep was very careful to explain that when expanding an R5 array, the array cannot be used until the rebuild finishes.