Soft-Raid Testing and other stuff...

[Richard Hobbs]

Hello,

> > I have built two RedHat 8.0 machines, both using soft-raid 
> to mirror one
> > 250GB disk onto the other identical 250GB disk inside the case.
> > 
> > During the install, I created the RAID partitions, and 
> assigned them to
> > actual partitions, and now I have "/dev/md0" up to "/dev/md7".
> > 
> > However, each time I boot and each time I shut down, I get 
> the following
> > message:
> > 
> >   No spare disk to reconstruct array! -- running in degraded mode.
> > 
> > What exactly does this mean? Both drives are visible from 
> the BIOS, and the
> > jumpers are set to Cable Select (not Master and Slave).
> > 
> > Despite the above error message, the machine boots fine, 
> shuts down fine,
> > and runs fine.
> 
> When it's up, cat /proc/mdstat

--------------------------------------------------
[root at stg-slave root]# cat /proc/mdstat
Personalities : [raid1]
read_ahead 1024 sectors
md7 : active raid1 hda9[0]
      71296320 blocks [2/1] [U_]

md3 : active raid1 hda8[0]
      2096384 blocks [2/1] [U_]

md4 : active raid1 hda7[0]
      10482304 blocks [2/1] [U_]

md6 : active raid1 hda6[0]
      73400832 blocks [2/1] [U_]

md5 : active raid1 hda5[0]
      73400832 blocks [2/1] [U_]

md2 : active raid1 hda3[0]
      7164864 blocks [2/1] [U_]

md1 : active raid1 hda2[0]
      7164864 blocks [2/1] [U_]

md0 : active raid1 hda1[0]
      104320 blocks [2/1] [U_]

unused devices: <none>
[root at stg-slave root]#
--------------------------------------------------
 
> > However, if I unplug the master hard drive, it will not 
> boot from the
> > secondary, even if I plug it into the primary socket on the 
> IDE cable.
> 
> Did you duplicate the MBR to the second drive?  If you 
> didn't, you won't
> boot.  Remember that you've only mirrored the data partitions, not the
> boot block.

I didn't duplicate the MBR as far as I know... I assumed that RAID 1
(mirroring) mirrored the entire disk, sector for sector...

If I duplicate the MBR successfully, does that mean I should be able to
simply remove the primary, and boot from the secondary alone?

Also, if I then insert a blank disk, will it automatically re-generate the
data onto it? Will I have to duplicate the MBR manually again?

Finally, how can I duplicate the MBR onto the secondary disk?

> > I have even tried inserting a third 250GB hard drive on the 
> secondary IDE
> > channel to see if that would become the spare disk it needs 
> to reconstruct
> > the array, but that didn't work either.
> 
> I wouldn't expect it to.  I would not be happy if the software just
> grabbed an extra drive and toasted the data on it unless I explicitely
> told it to.

Very true... It was a last ditch attempt to eliminate that if nothing
else... Lol

Thanks for your help Ed... I look forward to hearing from you again soon :-)

Hobbs.

-- 
Richard Hobbs (Systems Administrator)
Toshiba Research Europe Ltd. - Speech Technology Group
Web: http://www.toshiba-europe.com/research/
Email: richard.hobbs at crl.toshiba.co.uk
Tel: +44 1223 376964        Mobile: +44 7811 803377



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