Eric J. Feldhusen wrote:Example,
A computer with 4 - 100GB hard drives in a RAID 1 (mirroring), set up a mirror with 2 hot spares. Total storage - 100GB, but you can have 3 drive failures and the system can keep running.
In the event of two drive failures close together (second goes while rebuilding ), isn't there a small window of time that you'd only need to lose two to suffer complete data loss? Would it be better to have 3 active with one hot spare?
Excellent point, yes it would. I use the example below in practice, I tested the situation above in testing, but I wanted more storage space, so for the production server, I went with the raid 5 setup.
A computer with 4 - 100GB hard drives in a RAID 5 (parity) set up, 3 drives are active in the RAID 5, 1 hot spare drive, Total storage 200GB, actually a little less due to overhead. In this configuration, one of the drives in the raid fails, the hot spare becomes active, the raid rebuilds, and you replace the dead drive with a fresh drive and this drive becomes the hot spare. In this case, you can have 2 drives fail and the system can keep going.Same deal as above, what happens if a second drive fails during rebuild?
I haven't had it happen yet, but "in theory", with the setup above, it "should" continue to work, but you're really want to get another couple drives in that machine fast.