Hi all,
I'm looking for some advice about duplicating a RAID array on a seperate machine. I'm needing to move a client's server over to new hardware, and at the same time increase the disc sizes, so I've come up with a plan. I'm testing it in the morning, but I'd like to know if there's any glaring reasons why it won't work.

Basically, the existing system is running software RAID 1 on all its partitions. My plan is to hotplug a new (larger) drive into the old machine, and add its partitions to the RAID 1, so everything gets syncd. Once that's done, I hope to be able to fail the new drive, remove it and stick it into the upgraded server, along with another new drive, and rebuild the RAID, so that I essentially have a carbon copy of the old box but running on new hardware. All the partitions are ext3, so I should (hope to) be able to resize the partition filesystems using resize2fs.

AFAICT the hardware will be compatible (basically just faster CPU and more memory), but I'm wondering if the RAID will be able to rebuild itself on the new machine, particularly since the drive has been failed. When I fail the drive on the old machine and transfer, will (might) it boot? (Obviously it'll need grub installing on the MBR).

If I can get this to work, it'd be great, since we could cut server downtime to practically zero (albeit that when the new one is rebuilding its RAID it'll be dog slow).

Any and all comments welcome.

p.s. It'll all be done on fairly standard Debian etch systems

Well, no-one replied to this, but it worked. After numerous tests we had the transfer down to a tee. All that (we thought ) was required was a small change in the udev config, since the new hardware has different network card drivers.

We did the 'live' client restore tonight. Everything was fine until booting with the new hardware. It turns out someone had turned on a restore-from-swap package on the client's system (which we hadn't planned for). This caused the boot to fail, since there was no restore image in the hot-swapped swap partition. (If you follow ). Anyway, some frantic googling turned up that this is quite a common problem, but didn't really provide a fix. To avoid the restore-from-swap, you can boot with a 'noresume' kernel option, but by the time we'd figured that out, the RAID arrays were toast (although filesystem checks on the underlying partitions were clean).

Booting into knoppix and manually rebuilding the RAID with only one device (the hot-swapped drive's partitions in each case), then rebooting fixed it for us, and everything is working as it should.

While the total downtime was in excess of an hour (mostly while we scratched our heads wondering if we'd killed everything), this was still a lot better than the 5+ hours it would take to transfer over the network, plus altering the config files and everything else, with the added bonus that if it came to it we could stick the old machine back in unchanged.

All in all, RAID is great, and we know what to do next time.