[clue-tech] RAID5

[mike havlicek]

--- "David L. WiWillson<DLDLWillsonhTheGeekU> wrote:

> I have a 4x18 RAID array with a failed member. 
> There is little enough
> data, that I could just drop the failed member, and
> still have enough
> room.  It's formatted ext3.
> 
> I'd like to do everything hot, if I can.  Does
> anyone have advice before
> I begin?
> 
> _______________________________________________


Hello,

In July I had a similar problem with 4x9 SCSI2 disks
in a hardware RAID5 (internal to the server) losing
one of the disks. What I did was not a "hot" solution.
My situation was kinda quirky because my server was
compaq and the first disk in the array is "special"
and happens to be the one I lost. The system would not
boot properly with only 3 of the 4 disks where the
lost disk was the first in the array. The controller
would catch the problem with the array and one had to
hit an F key to get the server to procede in the boot
process... sigh...

I was using redhat AS4, so I booted into single user
mode from the install CD and did a level 0 dump of my
filesystems (unmounted) to tape first. Then I removed
the bad disk and physically rerearranged the disks,
rebuilt the RAID5 on 3 disks using using tools from
the controller card. 

My notes on the fiasco are a little sketchy. I think
because I was changing my partition scheme using LVM,
I did a minimal install of redhat. I then booted the
system into rescue mode from the install cd and for
each fifilesystem did a mkfs.ext3 followed by a
restore from level0 dump. The "new partitions" were
unmounted when putting the new filesystems on; and
mounted during tape restore. In my notes there is
something about problems that I had with the root
filesystem. It seems that I had problems unmounting
"root" under /mnt/sysimage using the umumount command
provided in rescue mode (the "lazy" umumount -l was
not working for me.) It seems that I ended up copying
the umount from the minimal install into /tmp from the
rescue boot and using that to "umumount -l" the root,
/mnt/sysimage to create the new root filesystem. There
were other things that had to be taken care of like
updating the grub configuration and fstab..

I admit that was pretty convoluted and probably not
the best way to go about things... but it worked... I
also admit that it took me a couple of tries to get it
working....

-Mike

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