Linux – Copy Linux host to new hardware

hardwarehplinux

I need to do host to host migrations from old hardware to new hardware. Specifically, from HP BL460G7 to HP BL460G8. Both the old and new servers have 2 x 600GB 2.5" drives and are configured for RAID1. I can afford 30 minutes downtime per server.

There are four servers to migrate, the smallest has a total of 120GB allocated in logical volumes and the largest has 510GB allocated. Three servers are running RHEL5 and one is running RHEL6.

I've been racking my brain on how to do this within the given time frame and without destroying the OS and critical data.

My only thought is this:

remove one drive from the old server (server is turned on)
remove both drives from the new server (server is turned off)
remove G7 drive from caddy and set aside
remove G8 drive from caddy and install into G7 caddy
install G8 drive in G7 caddy into old server
wait for RAID controller to rebuild RAID1 array
when finished shutdown old server
remove G8 drive in G7 caddy
install G8 drive in G8 caddy and insert into G8 (single drive installed)
boot G8 server
wait for OS to boot
when OS has booted insert remaining drive
wait for RAID array to rebuild

Does this sound sane?

EDIT: The RHEL5 are RHEL5.10 and the RHEL6 is RHEL6.6

I should have also noted that two of the systems are part of a hot four node cluster that does near constant replication of application "events" (its part of a critical infrastructure system). We have backups but we only use the in the event of total system failure.

Previous testing has shown about a maximum 'dd' between systems of around 50MBps which is far too slow.

EDIT: I was going to rely on kudzu to pickup and deal with the hardware changes.

Best Answer

It should be noted, that there may be other steps needed, depending on the distribution. Most notably the drivers (thanks for pointing that out @ewwhite).

Boot the new server from livecd/usb.
Prepare partitions and bootblock on the new drives.
- Depending on setup, this could be done by copying MBR/bootblock.
Make the filesystems.
Do an rsync from old server to new.
- You might want to do it again to see how long will the follow-up rsync take - if its under 30 minutes, continue.
- This is the time, you can actually try, if new system boots. Just be careful not to cause any IP (or other) conflicts.
Shutdown all services that would write to the filesystem
- Preferably reboot to livecd/usb
Rsync data from old server to new again
Reboot the new server and use it

Doing it this way, you still have the original server intact, so if anything goes wrong, there is an easy way back. But it requires some knowledge (grub/rsync/partitions), so I suggest doing some prep-work and testing in advance, before doing it live.

Related Solutions

Windows Server 2003 Hardware Migration – How to Best Migrate a Server to New Hardware

I do this often using StorageCraft ShadowProtect IT Edition. You can load in all the drivers for the new system before booting it.

Sometimes I've had luck with installing the storage drivers before migrating, and then going from there.

software-raid – Best Way to Grow Linux Software RAID 1 to RAID 10

With linux softraid you can make a RAID 10 array with only two disks.

Device names used below:

md0 is the old array of type/level RAID1.
md1 is the new array of type/level RAID10.
sda1 and sdb2 are new, empty partitions (without data).
sda2 and sdc1 are old partitions (with crucial data).

Replace names to fit your use case. Use e.g. lsblk to view your current layout.

0) Backup, Backup, Backup, Backup oh and BACKUP

1) Create the new array (4 devices: 2 existing, 2 missing):

mdadm -v --create /dev/md1 --level=raid10 --raid-devices=4 /dev/sda1 missing /dev/sdb2 missing

Note that in this example layout sda1 has a missing counterpart and sdb2 has another missing counterpart. Your data on md1 is not safe at this point (effectively it is RAID0 until you add missing members).

To view layout and other details of created array use:

mdadm -D /dev/md1

Note! You should save the layout of the array:

# View current mdadm config:
cat /etc/mdadm/mdadm.conf
# Add new layout (grep is to make sure you don't re-add md0):
mdadm --detail --scan | grep "/dev/md1" | tee -a /etc/mdadm/mdadm.conf
# Save config to initramfs (to be available after reboot)
update-initramfs -u

2) Format and mount. The /dev/md1 should be immediately usable, but need to be formatted and then mounted.

3) Copy files. Use e.g. rsync to copy data from old RAID 1 to the new RAID 10. (this is only an example command, read the man pages for rsync)

rsync -arHx / /where/ever/you/mounted/the/RAID10

4) Fail 1st part of the old RAID1 (md0), and add it to the new RAID10 (md1)

mdadm /dev/md0 --fail /dev/sda2 --remove /dev/sda2
mdadm /dev/md1 --add /dev/sda2

Note! This will wipe out data from sda2. The md0 should still be usable but only if the other raid member was fully operational.

Also note that this will begin syncing/recovery processes on md1. To check status use one of below commands:

# status of sync/recovery
cat /proc/mdstat
# details
mdadm -D /dev/md1

Wait until recovery is finished.

5) Install GRUB on the new Array (Assuming you're booting from it). Some Linux rescue/boot CD works best.

6) Boot on new array. IF IT WORKED CORRECTLY Destroy old array and add the remaining disk to the new array.

POINT OF NO RETURN

At this point you will destroy data on the last member of the old md0 array. Be absolutely sure everything is working.

mdadm --stop /dev/md0
mdadm /dev/md0 --remove /dev/sdc1
mdadm /dev/md1 --add /dev/sdc1

And again - wait until recovery on md1 is finished.

# status of sync/recovery
cat /proc/mdstat
# details
mdadm -D /dev/md1

7) Update mdadm config

Remember to update /etc/mdadm/mdadm.conf (remove md0).

And save config to initramfs (to be available after reboot)

update-initramfs -u

Best Answer

Related Solutions

Windows Server 2003 Hardware Migration – How to Best Migrate a Server to New Hardware

software-raid – Best Way to Grow Linux Software RAID 1 to RAID 10

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