[rhn-users] software raid

[Matt Allen]

On Monday 19 July 2004 11:03, Kvetch wrote:
> I have a machine with 2 identical IDE drives in them.  I know I can
> setup a software raid 0 partition which will enable a RAID mirror for
> that partition.  Is there a way I can setup software RAID 0 to work
> like a hardware RAID so it clones everything on the drive?  So can I
> just create one RAID device across the 2 drives and every partition I
> create under the RAID devices is duplicated on second drive, including
> the boot and / partition?  This way if either drive die I can work off
> one drive until the second drive is replaced?

First off, RAID 0 is striping, RAID 1 is mirroring. If you set up RAID 0 and 
lose one of your drives, all of your data is toast.

I don't know what release you're running, but under RHELv3 you use the RedHat 
partitioning tool (Disk Druid) to set up identical partitions on each drive. 
So, if you've got two drives and you want three partitions plus your swap, 
then create those three partitions on both drives, selecting the "Software 
RAID" option for partition type. (Note: You must create a swap partition on 
each drive, and they will not be involved in the RAID setup).

It should look something like this:

First drive:
/dev/hda1		software raid		10GB
/dev/hda2        software raid		8GB
/dev/hda3		software raid		5GB
swap

Second drive:
/dev/hdb1		software raid		10GB
/dev/hdb2		software raid		8GB
/dev/hdb3		software raid		5GB
swap

Once all of your Software RAID partitions are in place on both drives, select 
the RAID option and then create a RAID 1 device. Pick your mount point, FS 
type, and select two of the identical partitions (e.g, hda1 and hdb2). Repeat 
this step until all of your RAID devices are configured. 

You'll get something like this:

/dev/md0		ext3			10GB (mount point is listed somewhere)
/dev/md1		ext3			8GB
/dev/md2		ext3			5GB

I don't have Disk Druid in front of me so I can't check if all my terms are 
correct, and the layout of the information in Disk Druid is not identical to 
my notes above, but that is the gist of software RAID set up.

I haven't had a drive fail in any of my software RAID sets yet, so I don't 
know what recovery is like, but ideally you'd just run off of the good drive 
until you replace the bad, like you said.

Cheers,
Matt