Why can't I make a raid with multiple drives

[Red Squirrel]

I'm using centOS5, and trying to make a raid 5 with 3 500GB drives, but its telling me that it cannot span multiple disks. What's up with this? So is software raid out of the question if I want to use multiple drives? My plans kinda got blown.... wanted to do raid 5 with 3 drives to get a redundant 1TB drive. I know software raid is not recommended but figured I'd go the budget route and what I've read of it sounds good (and I'm sure I recall it mentioning multiple drives, hence the whole redundancy part)

 

[Red Squirrel]

Oh think I figured it out. Actually have to turn each individual drive into "software raid" format then after create the device.

 

[QuixoticOne]

Originally posted by: RedSquirrel
Oh think I figured it out. Actually have to turn each individual drive into "software raid" format then after create the device.

Yeah you need to use either DMRAID or MD based RAID.

google and man dmsetup
google and man mdadm

They are pretty much mutually exclusive.

once you decide to take control away from DM (if necessary) and you know what your devices are something like....

#!/bin/sh
dmsetup remove mpath0p1
dmsetup remove mpath0
echo DEVICE /dev/sdb /dev/sdc /dev/sdd > mdadm.conf
mdadm --examine --scan --config=mdadm.conf >> mdadm.conf
mdadm --assemble --config=mdadm.conf /dev/md0
mdadm --query --detail /dev/md0

can jump start assembling sdb and sdc and sdd (change to suit YOUR raid disc device names) into /dev/md0 and then you can use the normal mkfs.ext2 tools to make a journaled filesystem on /dev/md0 once it is assembled into the RAIDED md device.

IIRC that's more or less true for centos 5.1 as well as fedora (which is what I'm using ATM)... I've got a VM with Centos on it I can check some details on in a day or so if you have specific problems.