On Fri, May 18, 2007 at 11:21:55AM -0400, Phillip Susi wrote:
> Heinz Mauelshagen wrote:
> >Sure. The current code tries activating degraded mirrors with a
> >linear mapping. If that needs enhancement, please send patches.
>
> Ok, so to be sure: if dmraid finds only one disk in the mirror, it will
> activate it in a degraded state, and update the on disk metadata to
> indicate the state of the set is inconsistent? And there is no option
> to ask it not to degrade the set?
It activates the mirror degraded but doesn't update the ondisk metadata yet.
Use the BIOS to do that.
>
> Could you suggest a part of the source I might start looking at to add
> such an option?
format.c and activate.c.
>
> >>>Use "dmraid -r -c... device-path".
> >>I don't think this will do what I need it to. This will just read the
> >>metadata of the disk and report if that metadata says the set is ok or
> >>inconsistent. Presumably it will say it is ok because up until now it
> >>has been, but now we can't find the second disk to build the set so the
> >>state of the set needs changed to inconsistent.
> >
> >Well, you gotta find 2 drives for the mirror; if you only
> >discover one you can react on it.
>
> Huh? The -r option combined with the device-path argument tells dmraid
> to only look at that specific device, does it not? So it will read the
> metadata from that device and report what it says. Since the last time
> the raid set was active, it was ok, so the metadata on that disk will
> say the set is ok, but if you were to ask dmraid to activate the set, it
> would be degraded to inconsistent because one of the disks is missing.
>
> So what I need is a way to ask dmraid to assemble the raid set
> information from all discovered devices, and tell me if the set would be
> changed to degraded if activated now.
>
> >dmraid -tay ?
>
> Hrm... the man page does not explain the -t flag. Would -tay not also
> activate it? Or just test activating it? What sort of output would
> result if say, one of the disks is missing in the mirror?
Got to add a bit more.
It is the test option, which display the mapping information created
without trying the activation of the set.
dmraid -c ... -s ... might be another approcah for your issue.
>
> >>If the mirror IS activated by dmraid with one disk missing, does dmraid
> >>update the metadata to indicate that the set is inconsistent?
> >
> >Not yet. You'ld need to use the BIOS management util to do that for now.
>
> Whoa, that sounds like a data loosing bug. If dmraid activates the
> mirror in a degraded state, then the missing disk will become out of
> sync. Without marking the disk as inconsistent, if the other disk
> reappears when you reboot, the bios will activate the set thinking it is
> consistent when it really is not, which can lead to incorrect operation
> and data loss.
In that case you would have removed the drive and used the setup util
to fix things already. But yes, if you don't, you can get a problem.
--
Regards,
Heinz -- The LVM Guy --
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Heinz Mauelshagen Red Hat GmbH
Consulting Development Engineer Am Sonnenhang 11
Storage Development 56242 Marienrachdorf
Germany
Mauelshagen@xxxxxxxxxx PHONE +49 171 7803392
FAX +49 2626 924446
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
_______________________________________________
Ataraid-list mailing list
Ataraid-list@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/ataraid-list
