I have a software RAID5 array (Linux md) on 4 disks.
I would like to replace one of the disks with a new one, without putting the array in a degraded state, and if possible, online. How would that be possible?
It's important because I don't want to:
- take the risk of stressing the other disks so one may crash during rebuild,
- take the risk of being in a "no-parity state" so I don't have a safety net for some time.
I suppose doing so online is too much asking and I should just raw copy (
dd) the data of the old disk to the new one offline and then replace it, but I think it is theoretically possible...
Some context: Those disks have all been spinning almost continuously for more than 5.5 years. They still work perfectly for the moment and they all pass the (long) SMART self-test. However, I have reasons to think that one of those 4 disks will not last much longer (supposed predictive failure).