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Re: RAIDframe: what if a disc fails during copyback
On 10/29/20 11:33 AM, Edgar Fuß wrote:
(I could probably direct this question to oster@ instead of tech-kern@)
In a RAIDframe RAID-1, a disc failed and I reconstructed on a spare.
Now I want to replace the failed component (actually by the same disc,
which needed a firmware update) and want to copyback to it.
How will RAIDframe behave if, during the copyback:
1. The replaced component fails
This is a NOP, as it's already failed, and only the non-failed component
will be considered.
2. The spare fails
You're back to considering only the non-failed component.
3. The other, non-replaced component fails?
Since the rebuild is done, you can use the rebuilt component to continue on.
Specifically: Is there any szenario (other than more than one disc failing)
that will put the RAID into a non-redundant state? I guess 3. may?
2 or 3 will put you back to non-redunant.
However: You really don't want to be using copyback..... it's still
there, and it does work, but it's not at all performant or
system-friendly. Just put in the new component, reconstruct to it, and
then call it a day. If you want the components labelled nicely, give
the system a reboot (ya, not ideal, but that's where we are).
Basically the copyback code doesn't have the same IO structure as a
reconstruct, and behaves very poorly. Copyback should really be just
ripped out or at least ignored.
In your case, what I'd do is just fail the spare, and initiate a
reconstruct to the original failed component. (You still have the data
on the spare if something goes back with the original good component.)
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