Soft-Raid Testing and other stuff...

[Richard Hobbs]

Hello,

> -----Original Message-----
> From: redhat-list-bounces at redhat.com 
> [mailto:redhat-list-bounces at redhat.com] On Behalf Of Richard Hobbs
> Sent: 20 January 2005 10:02
> To: 'General Red Hat Linux discussion list'
> Subject: RE: Soft-Raid Testing and other stuff...
> 
> 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.

I have just found this web page...

  http://www.kieser.net/linux/raidhotadd.html

...and I'm currently following the instructions on it. So far, I have typed:

  > raidhotadd /dev/md1 /dev/hdb2
  > raidhotadd /dev/md0 /dev/hdb1
  > raidhotadd /dev/md2 /dev/hdb3
  > raidhotadd /dev/md5 /dev/hdb5
  > raidhotadd /dev/md6 /dev/hdb6
  > raidhotadd /dev/md4 /dev/hdb7
  > raidhotadd /dev/md3 /dev/hdb8
  > raidhotadd /dev/md7 /dev/hdb9

The current output from /proc/mdstat is:

--------------------------------------------------

--------------------------------------------------

This is looking more promising, but I don't think it's doing the MBR
still... Perhaps soft-raid doesn't work under RH8 as standard, otherwise it
wouldn't boot the disks from the array and cause me to have to manually
re-add them...

I shall keep you updated on how this goes.

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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