Bug#396582: Some additional info

[martin f krafft]

also sprach Dan Pascu <dan at ag-projects.com> [2006.11.03.2238 +0100]:
> But I'm glad you were able to at least see the problem I'm
> experiencing. One thing that intrigues me is why in my case when
> failing a drive and stopping the array, after restarting it, the
> failed drive was already removed (even though I never removed it
> myself) and the arrays started degraded with 1 drive out of 2, and
> in your case the array started with the failed drive included and
> reported that it started with 2 drives.

This only happens when the last update time stored in the failed
component's superblock is the same as the time in the other
components superblocks. Then mdadm says that the drive is failed but
looks okay. When I reproduced the problem, I saw exactly your
behaviour and did not have to remove the component.

Here's what I think happens exactly:

  - while the array is running, writes result in updates to the
    superblocks
  - if you fail a component, its superblock is no longer updated
  - when you stop/start an array, mdadm checks all the superblocks
  - if they all seem as if they'd been stopped at the same time, it
    just assembles.
  - however, if a superblock seems out of date, md writes:

      kernel: md: kicking non-fresh sde1 from array!

    and starts the array in degraded mode.

-- 
 .''`.   martin f. krafft <madduck at debian.org>
: :'  :  proud Debian developer, author, administrator, and user
`. `'`   http://people.debian.org/~madduck - http://debiansystem.info
  `-  Debian - when you have better things to do than fixing systems
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