Re: RAID5: mkraid --force /dev/md0 doesn't work properly

From: Evan Harris (eharris@puremagic.com)
Date: Mon Oct 01 2001 - 01:25:42 EST

Ok, thanks. I did that and it worked. But I have (unfortunately) one more
question about how raid disks are used. I've now remade the restarted the
raid, having left the oldest drive (/dev/sde1) as a failed-disk. I do a
raidhotadd /dev/md0 /dev/sde1, and this starts the raid parity rebuild and
gives this status in /proc/mdstat:

md0 : active raid5 sde1[6] sdi1[5] sdh1[4] sdg1[3] sdf1[2] sdd1[0]
      179203840 blocks level 5, 256k chunk, algorithm 0 [6/5] [U_UUUU]
      [=>...................] recovery = 8.4% (3023688/35840768)
finish=88.9min speed=6148K/sec

Now, my question is: the hotadd seems to have reordered the disks, so when
the rebuild is completed, do I need to reorder my raidtab to reflect this?
Like this?

        device /dev/sdd1
        raid-disk 0
        device /dev/sdf1
        raid-disk 1
        device /dev/sdg1
        raid-disk 2
        device /dev/sdh1
        raid-disk 3
        device /dev/sdi1
        raid-disk 4
        device /dev/sde1
        raid-disk 5

Or does the kernel still keep the drives in order as the raidtab already is,
even though they seem to be out of order in the syslog and /proc/mdstat? If
I have to force the recreation of the superblocks at some later point, which
way will keep the data from being lost?

Thanks. Evan 

-- 
| Evan Harris - Consultant, Harris Enterprises - eharris@puremagic.com
|
| Custom Solutions for your Software, Networking, and Telephony Needs

On Mon, 1 Oct 2001, Jakob Østergaard wrote:

> On Sun, Sep 30, 2001 at 07:51:25PM -0500, Evan Harris wrote:
> >
> > Thanks for the fast reply!
> >
> > I'm not sure I understand why drive 5 should be failed.  It is one of the
> > four disks with the most recently correct superblocks.  The disk with the
> > oldest superblock is #1.  Can you point me to documentation which explains
> > this better?  I'm a little afraid of doing that without reading more on it,
> > since it seems to mark yet another of the 4 remaining "good" drives as
> > "bad".
>
> Oh, sorry,   of course the oldest disk should be marked as failed.
>
> But the way you mark a disk failed is to replace "raid-disk" with "failed-disk".
>
> What you did in your configuration was to say that sde1 was disk 1, and sdi1 was
> disk 5 *AND* disk 1 *AND* it was failed.
>
> Replace "raid-disk" with "failed-disk" for the device that you want to mark
> as failed.  Don't touch the numbers.
>
> Cheers,
>
> --
> ................................................................
> :   jakob@unthought.net   : And I see the elder races,         :
> :.........................: putrid forms of man                :
> :   Jakob Østergaard      : See him rise and claim the earth,  :
> :        OZ9ABN           : his downfall is at hand.           :
> :.........................:............{Konkhra}...............:
>

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This archive was generated by hypermail 2b29 : Sun Oct 07 2001 - 21:00:13 EST