mdstat - what is this?

[Mike Reinehr]

On Saturday 30 September 2006 16:48, Michael Hipp wrote:
> Mike Reinehr wrote:
> > On Saturday 30 September 2006 08:08, Michael Hipp wrote:
> >> What's the md255 stuff below? I didn't create any such device.
> >>
> >> Thanks,
> >> Michael
> >>
> >> # cat /proc/mdstat
> >> Personalities : [raid1]
> >> md255 : active raid1 dm-4[1] dm-3[0]     <---
> >>        136351616 blocks [2/2] [UU]        <---
> >>
> >> md3 : active raid1 hdc2[1]
> >>        18787904 blocks [2/1] [_U]
> >>
> >> md2 : active raid1 hdc1[1]
> >>        104320 blocks [2/1] [_U]
> >>
> >> md1 : active raid1 hda4[0] hdc4[1]
> >>        136351616 blocks [2/2] [UU]
> >>
> >> md0 : active raid1 hda3[0] hdc3[1]
> >>        1044160 blocks [2/2] [UU]
> >
> > Michael,
> >
> > md255 looks suspiciously like md1. Have you tried using
> > `mdadm --query --detail /dev/md255` to learn more about it? Are there any
> > entries in your /dev directory named dm-?? Are you using udev? Perhaps
> > this is some peculiar behavior of udev.
> >
> > md now has persistent superblocks which will cause an array to be built
> > on boot-up whether you have it defined in /etc/mdadm/mdadm.conf or not.
> > Perhaps this is a leftover from some earlier raid array that you had set
> > up once, but did not erase the superblock (I think that's unlikely, too,
> > but you never know.)
>
> Thanks. The md255 ghost seems to appear at random and fade quietly away
> sometime later. It now looks like md0. This box has never had RAID on it
> - a severe oversight I'm in process of correcting. Anyway, it doesn't
> seem to be hurting anything so my pseudo-panic at seeing this interloper
> in my beautiful md stable was probably unfounded.
>
> Thanks,
> Michael

Michael,

If you're just now setting up RAID for the first time, I would like to make 
two suggestions, but accept my apology if you're already there & done. First, 
repartition & use cfdisk to set the partition type to (FD) Linux RAID 
Autodetect. And, two, use the newer raid tool mdadm to manage your RAID 
array. (Of course, you have to have to include md support in your kernel, 
too.)

Cheers & good luck!

cmr


-- 
Debian 'Sarge': Registered Linux User #241964

"More laws, less justice." -- Marcus Tullius Ciceroca, 42 BC