We have some servers that run in very harsh environments (research vessel) that need to have high-availability.
We have software RAID 1 for some measure of resiliency, along with proper data backups (tapes etc), however we would like to be able to break out a new server and re-image it (including RAID setup) from a known good copy if the hardware completely fails on the production box. Simplicity of the process is a big plus.
I am interested in any advice on the best way to approach this. My current approach (relatively new to Linux administration, totally new to MDADM) is to use DD to take a complete gzipped copy of one of the RAID'ed devices (from a live CD):
dd if=/dev/sda bs=4096 | gzip -c > /mnt/external/image/test.img
then reverse the process on the new PC, finally using
mdadm --assemble to re-create and re-build the array.
I'm not sure that this is the best approach, or if it will even work. Any advice would be great.
Best Answer
Your dd-based (block level) copy will include all the free space on the disk, won't take advantage of larger disks down the road, and won't fit onto smaller disks (in a pinch).
Rather than doing the cloning at the block level I'd do it at the filesystem level.
I'd boot the new server from the live CD, partition the disks, create the new MD array(s), format the arrays, run
mkswapon any swap volumes, then untar (or un-cpio, if you prefer) file-level copies of each of the source server's volumes into each of the new arrays. Finally I'd install the boot-loader. Then you're golden.All of that could be scripted and rolled onto a live CD/DVD image along with the filesystem archive(s) to untar.