Im tring to setup a Raid 5 disk system but im unsure of the partitions i need to get what i want.
I have x3 1TB sata hard disks and want to setup a Raid 5 system with them so that if any one of the 3 disks fail i can replace anyone, here is the partitions i have been playing with:
This works great if sdb or sdc fail, i can swap them with a different disk and rebuild them the problem starts if sda fails. When that happens i have booted from an OpenSUSE 11.1 Live cd and re partitioned the disk with the same three partitions and then rebuild the Raid on that disk. Then once you reboot the system it won’t boot from the harddisks. I guessed this might have something to do with Grub not been installed and pointing to the right disk. So booted back into the Live cd and tried installing Grub through Yast but it doesn’t seem to work. Also tried booting from a full OpenSUSE 11.1 DVD and used the repair system option, this however said i had no root partition. Im most confussed about what to do.
Any ideas how to fix this or if anyone has a better partition and Raid setup im happy to try that, can the /boot and /swap be put into the raid so if any disk fails it will be ok?
You could create a /boot on each drive (don’t mount the two extras) and
use dd to copy them across after the install is complete. You could
also setup additional swap and use all three in the fstab option (in the
partitioner) just set them as 1, 2 and 3.
eg;
sda1 swap pri=3
sda2 /boot
sda3 /data
sdb1 swap pri=2
sdb2 /boot_spare1 (do not mount at boot)
sdb3 /data
sdc1 swap pri=1
sdc2 /boot_spare2 (do not mount at boot)
sdc3 /data
Then use the following to coppy boot to the spare ones;
Im using this for a server that will be a media streamer to my PS3 and as there will be loads of video on there i wont be able to back it all up so having a Raid 5 is the next best thing.
So if disk one fails i could just enable the /boot on the other disks and i would boot ok?
Hi
Yes syslinux is part of the distro either from YaST or command line
zypper in syslinux. This can be all done after the install, and
probably best from rescue mode so the disks are unmounted, just need to
copy that mbr.bin to one of the boot directories and mount that
manually.
Like I said, wait for comments from others first, this can all be done
later after you install…
Ok im still have problems with my setup. I have now tested the following setup:
eg;
sda1 /boot
sda2 swap pri=3
sda3 /
sda4 /data
sdb1 /boot
sdb2 swap pri=2
sdb3 /
sdb4 /data
sdc1 /boot
sdc2 swap pri=1
sdc3 /
sdc4 /data
md0 raid 1 using the 3 partitions for /boot
md1 raid 5 using the 3 partitions for /
md2 raid 5 using the 3 partitions for /data
This installs and runs fine. Now if sda fails the system still boots because sdb becomes sda and as it has a mirror of boot on there it boots fine. This is better than i was getting before the problem starts when you try to connect a new disk back as sda, the system won’t boot because sda is blank. So i booted from a OpenSuse Live cd and recreated the partitions on sda and then reconstructed the raid on the new disk, this all worked fine and the raids are all happy. Now if you reboot the system you would expect because of the mirror for /boot grub would be there working fine and you would boot off sda, this doesnt happen and im left with a black screen and “Booting from local disk”.
Ok so i then tried to boot the System repair from the DVD and reinstall Grub, this returns the error that no root partition is configued and won’t install a grub config. So i checked the Partition setup in the system repair tool and it doesn’t show any of my raids i have setup, the partitions are all there but none of the raids yet in the Live cd they are all there. So i tried to create them but not mount or format them, it lets me do this but them it seems to be reconstructing the raids as the disk are going for it then click accept and i get an error and are thrown out of the system repair!!! Is this happening because the System Repair isn’t mounting these Raids.
Any ideas on how to recover if the first disk in an array fails or is this just not possiable?
Hi
I’m guessing it doesn’t boot because sda hasn’t re-synced. Just let it
boot from sdb/c (switch the disk order in BIOS) and let it re-sync,
then if a disk fails just swap for another and move on
I wouldn’t have raided the boot partitions just kept the spare ones
there and available (and unmounted), also in this scenario you need to
use the dd command after a kernel update.
Hi
Another thought check the fstab and make sure the disks are mounting by
device label not the device id, so if you change disks it doesn’t get
all confused.
Ok im going to try what you recommend with the /boot partition not raided and on each disk. WHen you say /boot do you just mean the /boot or do you mean the whole of / ?
Rebooted and pulled disk one. The system doesn’t boot, which i expected because sdb1 /boot isn’t set to be mounted.
So i installed new disk and booted from the Live cd, recreated the 4 partitions on the disk and copied the /boot back from sdb1 to sda1 using the command:
dd if=/dev/sdb1 of=/dev/sda1
I didn’t reconstruct the raids on sda but as this is a raid 5 the /boot partition should mount into the raid md0 and the system should boot. Or im i asking to much here?
Now rebooted and expected the system to boot from sda1 however it doesn’t, so im stuck again.
I have tested what you have suggested i dd the mbr and installed syslinux after i had installed the system by booting from a live cd. Then removed the 1st disk and replaced with another. Booted from a the live cd rebuild the partitions and the raid. dd the /boot partition back over and then booted from the hard disk and it won’t boot. Rebooted from the live cd and had a look at the /boot folder and it has no /grub folder so it has nowhere to boot from. Tried to reinstall /grub on the command line but this returns errors???
Have i missed something out or done something in the wrong order?
