[nzlug] LVM and toast....

[Nevyn]

On 4/2/07, Nevyn <nevynh at gmail.com> wrote:
> On 4/2/07, Daniel Pittman <daniel at rimspace.net> wrote:
> > Nevyn <nevynh at gmail.com> writes:
> >
> > > Nevermind - turns out that the raid device isn't starting as I'd hope.
> > > It's showing 2 disks as spares. There was a command suggested in a few
> > > places but they haven't helped at all.  mdadm --assemble --force
> > >
> > > The only other reference I found to try and fix this error said the
> > > following: Rewrite the RAID superblocks by mkraid --force
> > >
> > > Unfortunately raidtools is no longer in Ubuntu.
> >
> > Anything that advises using raidtools is *bad* advice these days:
> > mdadm will do anything they can do, better, faster, stronger, etc. ;)
> >
> > Anyhow: if the RAID was completely stopped and you ran 'mdadm --assemble
> > --force' without effect there are two paths open to you:
> >
> > You could ask on the Linux RAID mailing list where Neil Brown is both
> > active and helpful.  If this can be resolved you will not get a more
> > authoritative answer.
> >
> >
> > Secondly you could just get ... brutal about it: if you create a new
> > RAID array with the same settings, components and device order as the
> > first array everything will "just work."
> >
> > Of course, be warned: GET IT WRONG AND YOUR DATA IS TOAST! DEAD! GONE!
> >
> > Ahem.  Anyway: Linux software RAID uses the superblock at the end of the
> > disk to manage devices -- there is nothing else it cares about.  So, the
> > effect of this is to ignore the old superblock and create a new array
> > with the existing data in place.
> >
> > NOTE: You may need to pass additional arguments to mdadm to prevent
> > recalculation of parity blocks for RAID levels that use them.
> >
> >
> > Anyway, once the new RAID array is in place and correct the data should
> > be ready for you to fsck and go back to using as expected.
> >
> > Regards,
> >         Daniel
> >
> > I would, personally, go for the mailing list option first. :)
>
> Thanks Daniel. The second option though wouldn't be TOO bad except
> trying to get the details just right. They're whole disk partitions
> and everything so it's just a matter of getting the details right...
> Device order I think is the one that I'm likely to trip up on - is the
> device order the same as the order shown in /proc/mdstat?
>
> Anyway, that's academic for the time being. I've subscribed to the
> linux-raid list and so will get back to that option if I need it.
> (Last ditch attempt)
>
> Regards,
> Nevyn.

Got a tad impatient as I hadn't had any responce on the linux-raid
list. Anyway, attempted to get it going and it's now really toastly
like. Thanks for the suggestions guys.