[K12OSN] Re: how's this raid setup?

Robert Arkiletian robark at gmail.com
Fri Sep 2 06:50:33 UTC 2005


On 9/1/05, Les Mikesell <les at futuresource.com> wrote:
> 
> 
> Grub doesn't even install correctly on the first drive of
> a RAID1 with Centos. Fortunately it is not difficult to



You would think it should set it up right on the first drive at least!?!? 

do it by hand and you only have to do it once. You
> can either ctl-alt-F2 to a shell prompt at the end
> of an install before the reboot or boot from the
> install cd with 'linux rescue' and chroot to /mnt/sysinstall
> after it mounts the drives for you. Then:
> 
> grub
> > device (hd0) /dev/sda
> > root (hd0,0)
> > setup (hd0)
> > device (hd1) /dev/sdb
> > root (hd1,0)
> > setup (hd1)
> > quit
> 
> If you are in rescue mode, exit twice to reboot.
> 
> That assumes scsi disks and /boot as the first partition
> of each. Whether it works in practice or not will depend
> partly on how the drives fail. Some failure modes will
> still hang the system. If you simulate a failure by
> removing the 1st drive in a scsi system, it will usually
> boot from the 2nd but all the device names will shift
> up so your swap or other unlabled partitions may land
> in the wrong place.
> 

Wow thanks for the excellent reply Les! I was thinking of four primary 
partitions having both sda and sdb exactly the same.(36 GB each)

/ 13 GB
/home 20 GB 
/var 2 GB
swap 1 GB (since I've got 4 GB of ram and I never hit swap)

So if sda failed, would the swap on the second drive shift? BTW I thought 
multiple swap partitions on seperate drives automatically use raid 0. So do 
I need to state that they are a raid device? Wait I just thought about this 
for a second. I think they HAVE to be defined as a raid1 device. Assume you 
go into swap then one drive fails. If it's raid0 you are going down 
bigtime!! So I think they have to be explicitly defined as a raid1 device.

-- 
Robert Arkiletian
C++ GUI tutorial http://fltk.org/links.php?V19
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