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?
Could you suggest a part of the source I might start looking at to add
such an option?
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?
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.
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