on 3-31-2008 6:30 AM Toby Bluhm spake the following:
Mail Administrator wrote:
Thnaks john,
u gave me a grt idea .. the second one seems quite interestin
but i do have to get additional HDD and mirror my existing server which has jus one disk
This was my procedure to mirror an existing single IDE disk RH4 system.
YMMV. No guarantees. Not tested on Centos5. May eat all your data and drink all your beer.
Make a total backup before doing anything.
IIRC the grub setup is what gave me the most problem.
Hopefully, someone will chime in to point out any flaws here.
Current System/OS on single 10GB IDE disk /dev/hda2 = swap @ 1GB /dev/hda1 = / @ 9GB Current system/OS is not in an LVM volume.
- Install a 2nd identical disk as hdb
- fdisk:
/dev/hdb1 = 9000M ; /dev/hdb2 = 1000M ( rest of disk ) part1 = type FD (raid) part2 = type FD (raid) 3. Create mirror device /dev/md10 for / with 2nd disk missing: mdadm --create --level=1 --force --raid-devices=1 /dev/md10 /dev/hdb1 4. mke2fs -j /dev/md10 5. Create mirror device /dev/md11 for swap with 2nd disk missing: mdadm --create --level=1 --force --raid-devices=1 /dev/md11 /dev/hdb2 6. mkswap /dev/md11
It may be safer to start step 7 from a rescue disk.
- mkdir /z
- mount /dev/md10 /z
- cd /
- dump -a0f - . | ( cd /z ; restore -xvf - )
- Update pertinent lines in
/z/etc/grub.conf: splashimage=(hd0,0)/boot/grub/splash.xpm.gz root (hd0,0) kernel /boot/vmlinuz-2.6.9-11.EL ro root=/dev/md10 rhgb
/z/etc/fstab: /dev/md10 / ext3 defaults 1 1 /dev/md11 swap swap defaults 0 0
- Shutdown
- swap hdb & hda around
- Boot RHEL4 linux rescue ; let system find/mount RHEL Installations
- fdisk hdb to be identical to hda
- chroot /mnt/sysimage
- grub-install /dev/hda
- grub-install /dev/hdb
- Setup grub:
grub root (hd0,0) setup (hd0) quit 20. Create new initrd(s) to include modules raid, scsi, lvm, etc needed at boot time: mkinitrd --with=raid0 --with=raid1 --with=raid5 --with=aic79xx /boot/initrd-2.6.9-22.EL.img.new mv /boot/initrd-2.6.9-22.EL.img /boot/initrd-2.6.9-22.EL.img.old cp /boot/initrd-2.6.9-22.EL.img.new /boot/initrd-2.6.9-22.EL.img 21. Reboot to normal startup on the new mirrored / & swap.
Step 21 needs to boot cleanly. Step 22 will remove your last chance to revert to the old setup by installing the original boot disk as hda. If something goes bad here, may need to restore from backup.
- Add in 2nd disk to md10 mirror set:
mdadm --grow /dev/md10 --raid-devices=2 mdadm --add /dev/md10 /dev/hdb1
- Add in 2nd disk to md11 mirror set:
mdadm --grow /dev/md11 --raid-devices=2 mdadm --add /dev/md11 /dev/hdb2
You can monitor the sync process:
cat /proc/mdstat: md10 : active raid1 hdb1[2] hda1[0] 8789632 blocks [2/1] [U_] [>....................] recovery = 0.8% (77952/8789632) finish=5.5min speed=25984K/sec unused devices: <none>
- System will be at normal state when mirror sync is finished
One thing to add. Don't put the second drive as a slave to the first. Most times when a PATA drive goes down it will lock the entire channel until a reboot. The whole point of having the mirrors is to keep running on a drive fail. It is better to have it on the secondary master as hdc. Of course this doesn't apply to SATA or SCSI or their variants