also, what about a mirrored raid? is it possible to create one
without having to start from scratch and reinstall? like just add the
drive to mirror to and mirror it? what would be the best solution for my
situation?
The advantage of RAID is that you have an always-up-to-date copy of your disk. You can transfer your existing install to a RAID configuration, but it involves doing a full file-by-file copy. The procedure goes along the following:
- Perform a backup of your important data. Just in case.
- Do an orderly shutdown of your system.
- Install your new hard drive. Put it on another channel than the first drive (for example, if your first hard drive is hda, install the new drive on the second channel, as either hdc or hdd). The following assumes it is hdc.
- Boot from a liveCD (e.g. Knoppix).
- Insert the raid1 module:
# insmod raid1
- Partition your new disk to have approximately the same layout as the old one. Set the partition type to fd (Raid autodetect):
# fdisk /dev/hdc
- Create new (degraded) md devices for every partition, with two devices, one being a partition of your new disk, and the other one marked as missing:
# mdadm --create /dev/md0 -l 1 -n 2 /dev/hdc1 missing
# mdadm --create /dev/md1 -l 1 -n 2 /dev/hdc2 missing
...
- Create filesystems on the new md devices, for example ext3 or swap:
# mke2fs -j /dev/md0
# mkswap /dev/md1
...
- Mount both the old disk and the new md devices, and copy the content of all partitions from the old disk to the new one:
# rsync -avH /mnt/hda1/ /mnt/md0
...
- Edit a few strategic files (fstab, lilo.conf or grub.conf, etc) on the md devices to reflect that your new root filesystem is on /dev/md? instead of /dev/hda?
- Do a poweroff.
- Swap both hard drives. From now on, your old disk is /dev/hdc and your new disk is /dev/hda.
- Re-boot into the liveCD, re-insert the raid1 module, re-mount your md devices.
- If you use lilo, re-run it on the md device:
# lilo -r /dev/md0
- Reboot, but without the liveCD, this time. You should boot into the same system as before you started, except it is now running from a degraded RAID1.
- Check that *everything* works as expected. Do a real *thorough* test, because the next steps will wipe all the data on your old disk.
- Partition the *old* disk to have the same layout as your new disk. If the partition sizes don't match exactly, create them slightly bigger than on your new disk. Also set the partition type to fd.
- Hot-add the partitions from your old disk to the degraded RAID devices:
# mdadm /dev/md0 -a /dev/hdc
- Re-run lilo if that's your bootloader.
- You can watch the reconstruction process with:
# watch -n 10 cat /proc/mdstat
- Et voil�! Your existing install has been tranfered to a RAID1 system.
I have performed this operation several times, and it works like a charm. Note that this is all from memory, so I might have missed a few points. I would suggest you only embark on such a procedure if you fully understand what happens at every step, and are prepared to improvise in case I have missed something.
HTH. -- Remy
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