CentOS - May 2005 - problem with swap and upgrade to 4 from 3.3

Dear All,

I've tried to upgrade a Centos 3.3 installation to 4.0 using YUM and 
some instructions I found in a thread on the Centos Forum.

The initial problem I had with Python 2.3/2.2 has been resolved, and now 
I am trying to upgrade the kernel to 2.6 prior to the yum upgrade, 
unfortunately it bails out at the end with dependancy erros on Xfree86. 

At this point I decided to use the CDs with a the "upgradeany" option.
This went fine initally but then bails out with a swap error, this is 
because swap on this machine is on /dev/md2 (a mirrored set) and this 
was not set up at the original install time, as all the other partitions 
were:  when the machine was installed, one of my staff did not set the 
swap up mirrored, so I had to mirror the swap partition manually after 
the original install.  This works fine, but the machine cant enable the 
swap at boot becuase it does this prior to enabling the RAID subsystem, 
so the swap startup fails, but once the machine is up, the swap is 
actually running without any manual intervention.  Its this error, that 
stops anaconda from upgrading the OS from the CDs

I note on other machines I have installed when the swap was mirrored on 
the original install, it still appears to enable swap prior to the RAID 
subsystem, without any errors.  So I guessed this might be a problem 
with the ram disk image, so I created a new one using mkinitrd, but the 
swap still fails at startup, thus preventing me from using the CDs to 
upgrade the box.

I guess I could set the swap back to an unmirrored set, run the upgrade 
from the CDs then mirror it again, but this is not ideal, does anyone 
have any suggestions as to how to fix this little RAID niggle with the 
swap caused by not RAIDing the swap parition originally on install?

Regards

Pete

Hey Peter,

Peter Farrow wrote:
> I note on other machines I have installed when the swap was mirrored on 
> the original install, it still appears to enable swap prior to the RAID 
> subsystem, without any errors.  So I guessed this might be a problem 
> with the ram disk image, so I created a new one using mkinitrd, but the 
> swap still fails at startup, thus preventing me from using the CDs to 
> upgrade the box.
> 
> I guess I could set the swap back to an unmirrored set, run the upgrade 
> from the CDs then mirror it again, but this is not ideal, does anyone 
> have any suggestions as to how to fix this little RAID niggle with the 
> swap caused by not RAIDing the swap parition originally on install?
I wouldn't personally recommend using software raid on swap partitions 
since it causes all sorts of problems like you're describing. If you 
want to get raid type performance from your swap partitions, I'd suggest 
just letting the kernel itself handle that.

All you need is to define each of the swap partitions in your /etc/fstab 
like so:

/dev/sda3       swap           swap    defaults,pri=1   0 0
/dev/sdb2       swap           swap    defaults,pri=1   0 0
/dev/sdc1       swap           swap    defaults,pri=1   0 0

That would set up parrallel swap on 3 scsi disks and might get you 
through your problem..

HTH

Dan

From: Peter Farrow <peter at farrows.org>
> Hi There,
> Yes I agree, I always raid the swap.....when the original install was 
> done a staff member (who I have now fired :-) ) did not raid the swap 
> partitions at install time, leaving me with this problem after raiding 
> them subsequently
Definitely.

Although one should _avoid_ RAID-5 and, in the worst case, consider RAID-3 or
RAID-4,
if RAID-1 or RAID-0+1 is not possible.



--
Bryan J. Smith   mailto:b.j.smith at ieee.org