Hello,
I have been trying to get a software raid configuration working for a
few weeks with little success.
I currently have a 3ware 7506-4 card with 4 drives. The raid 5
performance of this card is poor and it was recommended to me to try
using the card as a JBOD controller and running software raid on top of it.
I am currently running FC6 on this machine.
Here is what I have tried:
1) Backup the machine
2) Boot from knoppix DVD
3) Partition the drives using fdisk into 4 partitions. 100M for /boot (
bootable ), 2048M for swap, 16384M for /, and the rest for /export. All
partitions were tagged as 'fd'
4) Use sfdisk -d to copy the exact partitions to all 4 drives
5) Use mdadm to create md0 as raid 1 for /boot ( first two disks ),
md1-3 as raid5 with no spares ( all four disks )
6) Restore /boot, /, export
7) mkswap /dev/md1
8) update fstab and grub.conf to reflect new partitions ( chrooted )
Here is where I get lost and confused
I tried to chroot into the old image mounted completely under
/mnt/sysimage. I ran grub-install on /dev/sda and /dev/sdb. It
complained about /dev/sdb not being a bios drive ( or similar ). I
figured that was ok and I could fix it later.
Upon reboot, grub was definitely in sda, but it failed to boot
complaining it couldn't find stage1 files.
I tried to boot from Redhat rescue DVD. It sees a 4 disks, but the raid
comes up without sda. I can do a dmesg and see sda, but the raid says
it is missing. It looks like Redhat thinks there is a /dev/dm_* devices
as well. However, these disks have no lvm on them.
Rebooting into Knoppix now shows the array is in degradated mode.
/dev/sda is being thrown out..but I can't remember the exact error.
Googling showed that I needed use mdadm to fail sda, remove it, and
re-add it. However, mdadm wouldn't remove it because it said it was
busy. I am assuming this is related to same issue as the Redhat rescue
issue.
The software raid seems a little fragile as well. If I have my external
drive plugged in and all devices shift ( sda-d become sdb-e) when
booting from Knoppix which seems to cause problems as well. I thought
with all the data being written to the superblocks it would handle this
problem.
So, I am looking for a little guidance in where I am going wrong. It
takes about 24 hours for me to make this work and restore if it goes
badly so I am a little hesitant to play to much without figuring out a
correct path.
In the end, I went back to hardware raid on the 3ware card which works
perfectly, just abysmal performance.
Any thoughts or suggestions?
Michael
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