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So last year I helped my father in France set up his Office machine with a RAID5 array of 3 identical 1TB drives (for a combined space of 2TB). Last week one of the drives died, he's using the machine in degraded mode but I'd like to get that sorted ASAP.
The thing is after he got a replacement drive he put it in and the system doesn't recognise there is a physical drive there. After some testing with cables and both the original drive and the replacement we've come to the conclusion that the motherboard has stopped recognising that connection.
The system currently has a small drive it boots from and the raid array is then mounted on /home. It's got 4 SATA slots, 3 taken up by the boot drive and the two working parts of the array and the fourth being the one that's died.
Without replacing the motherboard and having to take into account that I'm in England and he's in France so I can't just pop round and try stuff out my thought is to fall back to RAID0. He loses the redundancy but keeps the same amount of space which to my mind means it should be possible (moving to a 1TB RAID1 array seems out of question).
But I've generally not had to deal with such matters, I'm more of a developer, can someone tell me if it's possible to go from RAID5 to RAID0 in place or will I need to wipe it, rebuild it and the copy the data back from a backup?
Thanks. I hope there's enough information here.
According to the section Grow Mode in man mdadm, it is possible, but you need space for a backup file. I couldn't find any information on how big the backup file needs to be.
– Dennis – 2013-03-15T16:25:45.647To be honest, a degraded RAID5 array (like what you have now) is mathematically comparable to a RAID0 (stripe). You lack the redundancy, and the data is striped. The giant drawback is that you have to compute checksums, so performance is lower than a stripe. – Mutant Bob – 2014-03-07T16:22:23.730