David Rees wrote:
I've got an 8 disk RAID10 array (near2 layout) where I am moving data off some older disks onto newer disks. Currently what I'm doing is adding the newer disks as spares and then failing/removing the older disks one at a time. This works fine, but leaves me with an hour or so of running the array degraded while the spare drive syncs up which leaves me open for data-loss during this time period. It seems like I should be able to add a drive as a directly replacement for one of the drives I'm pulling out (so I temporarily end up with 3-copies of that chunk instead of 2) until I pull fail/remove the older disk. If I was using RAID0 striped over RAID1 mirrors, for example, I know this is possible. Is this possible to do with RAID10?
In a slow, ugly, complex way, as someone described in another response. It involves using raid-1, and I suggest checking the write-mostly option as well, and involves some short time without the 2nd copy configured (and using check may not test everything on raid-10). Use a bitmap if you're not already.
There is at least one other current thread regarding the need for a "clone member" feature in md, but unless someone with time and skills also has the problem, I doubt it's going to get added soon.
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