ProxMox 3.x RAID-1 Transfiguration

Proxmox 3.2 RAID-1 Conversion - GPT Mode - With Bonus Features!

The latest Proxmox can install as GPT.  Not sure if we have any say in the matter.  BUT, in case you had a die-hard need to convert your Proxmox server to RAID-1, this is a cleaned-up set of instructions.  YMMV, make sure you backup your data, check your particular partition configuration, and READ CAREFULLY.  Also it is important to note that gdisk and sgdisk will be your friend, fdisk and sfdisk will not.

Basis: http://boffblog.wordpress.com/2013/08/22/how-to-install-proxmox-ve-3-0-on-software-raid/

EDIT and RAID-5 NOTE:
This site describes some changes you need to make to get RAID-5 working.  The below is good for RAID-1 only.  The important distinctions come with the initramfs modules.  I'll try to put together another post that sums all this up....or you can just go here:

• http://terraltech.com/how-to-install-proxmox-ve-3-1-with-software-raid5-using-mdadm/#.VKMKTXVGjUY

Notes:
It is necessary to either have a valid license or to manually configure apt to use another set of repositories.  Otherwise, mdadm will not be available.  Details at:
https://pve.proxmox.com/wiki/Package_repositories

Instructions:

• Duplicate partition info onto new drive:
• sgdisk -b sda-part.txt /dev/sda
• sgdisk -l sda-part.txt /dev/sdb
• Configure partition types as RAID members:
• sgdisk -t 2:fd00 -t 3:fd00 /dev/sdb
• NOTE:  partition 1 must be type EF02 to support GRUB.  DO NOT TOUCH THIS PARTITION!
• Create RAIDs:
• boot
• mdadm --create /dev/md0 -l 1 -n 2 missing /dev/sdb2
• root
• mdadm --create /dev/md1 -l 1 -n 2 missing /dev/sdb3
• Copy /boot
• mkfs.ext3 /dev/md0
• mount /dev/md0 /mnt
• rsync -avsHAXS /boot/ /mnt/
• ## Update fstab with new boot mount: /dev/md0 (don’t use UUID)
• reboot
• Configure mdadm.conf
• mdadm -D --brief /dev/md0 >> /etc/mdadm/mdadm.conf
• mdadm -D --brief /dev/md1 >> /etc/mdadm/mdadm.conf
• Update GRUB & initramfs
• echo 'GRUB_DISABLE_LINUX_UUID=true' >> /etc/default/grub
• echo 'GRUB_PRELOAD_MODULES="raid dmraid"' >> /etc/default/grub
• echo raid1 >> /etc/modules
• echo raid1 >> /etc/initramfs-tools/modules
• grub-install /dev/sda
• grub-install /dev/sdb
• update-grub
• update-initramfs -u
• Convert BOOT partition to RAID-1
• sgdisk -t 2:fd00 /dev/sda
• mdadm --add /dev/md0 /dev/sda2
• Migrate all logical extents to /dev/md1
• pvcreate /dev/md1
• vgextend pve /dev/md1
• pvmove /dev/sda3 /dev/md1
• …. wait a long time ….
• vgreduce pve /dev/sda3
• pvremove /dev/sda3
• Convert sda3 to RAID
• sgdisk -t 3:fd00 /dev/sda
• mdadm --add /dev/md1 /dev/sda3
• …. wait a long time ….
• Reboot for final test - everything should work!
• Configure monitoring, device scans, emails, etc
• Configure SMART
• SUCCESS!!

Now you have a server that can tell you a little sooner that it might die, and have a better chance of recovering from said-death.

Why This Works:

Ordinarily, pv-moving from one partition to another of the exact same size doesn’t work, except (in our case) when the partition isn’t actually 100% in use.  As it turns out, Proxmox leaves a little extra at the end, maybe for snapshots, and consequently we can move from our original PV to one that is 1 LE smaller without issue.

Using the above technique, it should be perfectly possible to migrate to a different array configuration, such as RAID-5 or RAID-6, if you have the drives for it.  Just make sure that you load the appropriate modules into GRUB and initramfs.  All other commands should be similar, and of course there will be more of them (because there will be more drives to configure).

Why You Might Want This:

Software RAID is not officially supported by Proxmox, so you are on your own there.  BUT, if you do trust mdadm (and who doesn't?), you can have your RAID and use it, too.  There are no hardware adapters to buy, or to fail, or to curse at when they fail to read the metadata from one or more of your disks during some random reboot.  If you are very concerned about data integrity, then you should be looking at ZFS-backed iSCSI stores instead of mucking around underneath Proxmox's hood.  That said, having this all running RAID-1 does make recovery a heck of a lot easier, and especially if you couple it with a ZFS iSCSI store for all your actual VM data.

And remember:  RAID is NOT a backup solution.  If you treat it like a backup solution, you have no one but yourself to blame when all your data gets toasted after a multi-drive failure, fool!