tech-kern archive

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Old Index]

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.)


Greg Oster

Home | Main Index | Thread Index | Old Index