My lab is considering setting up a server with an attached RAID device for storing our large imaging datasets. (probably a Mac Mini server with attached Promise SmartStor DAS w/ 4 1TB hard drives)
Since there will be 4 1 TB hard drives, I would like to set up a RAID 1 configuration where 2 of the drives (say, A and b), will be mirrored onto the other two (say, C and D).
Here are the questions:
1) Is my understanding of RAID 1 correct to do the above?
2) If, for instance, drive A fails, the mirrored drives will immediately take over, right?
3) When such a failure occurs (such as when A fails), will swapping it for a new empty hard drive (a new, drive E) be all that I need to do? That is, will the still functioning mirrors (C and D) automatically be used to rebuild the new drive (E)? Is this something I should set up in the server software?
4) Hypothetically speaking: suppose I disconnect one of the drives, say B, and connect it to a separate computer, add/remove a few files, plug it back into the RAID 1 group, will this screw things up?
Thank you very much!
Answer
That storage box you mention only support RAID levels 0, 1 & 5, not RAID 10 (i.e. the mirroring of multiple striped disks you mention in your second paragraph).
That said the basic idea you mention is right, in that in the event of a single disk failing (being pulled out manually is effectively a failure) then the other side of the mirror would continue to work. Inserting a new working disk does indeed initiate an array rebuild, which when complete would be capable of allowing the array to survive another disk failure.
Oh and your "4)" would definitely screw it up.
I'd be tempted to buy a RAID 10-capable box by the way, oh and make sure it supports Firewire 800 as that's the fastest external interface you have available on a MacMini.
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