Red Hat Bugzilla – Bug 196124
partitionable raid (/dev/md0p) support
Last modified: 2007-11-30 17:11:35 EST
Description of problem: Anaconda currently supports only regular RAID devices (/dev/md0), which provide just a single volume or partition. This forces a minimal RAID installation to: - create partitions on /dev/sda and /dev/sdb - create two raid devices, /dev/md0 and /dev/md1 - set up /boot on /dev/md0 and LVM on /dev/md1 on drive failure, the user is forced to recreate the partition table on the new disk, and rebuild the two RAID arrays. In contrast, if partitionable RAID were supported, installation, recovery, would be much simpler and more intuitive. Installation: - create /dev/md0p from /dev/sda and /dev/sdb - partition /dev/md0p - create /boot and LVM Recovery: - add the new /dev/sdb to the array; the partition table is part of the array and therefore mirrored automatically Version-Release number of selected component (if applicable): anaconda-11.0.5-1 How reproducible: always Steps to Reproduce: 1. install on a machine with two disks 2. groan as you are forced to duplicate the RAID setup for every partition you create 3. cry when you have to partition your new disk and hot-add every partition when you recover Actual results: tears Expected results: happy smiles as you create, managem, and recover just one RAID device for all partitions
If this is implemented, a new feature becomes easy to implement: RAID retrofit. Currently, if you install a system without RAID, then add a disk, it is impossible for the average user to mirror the two disks. If partitionable RAID support is added, we could default to setting up partitionable RAID even with a single disk. If, later, a disk is added, one command will add it to the RAID.
LVM already gives you the ability to partition the RAID device... adding support for another way of doing things is just likely to a) make the UI even more confusing and b) make it more likely for things to fail in unexpected ways.
LVM can parition a RAID device, but one cannot boot from LVM; this means you need at least two RAID devices _and_ the old msdos partitioning. It will make the UI a lot _less_ confusing if you hide the non-partitionable RAID behind some 'advanced' button and make partitionable RAID the default. I recently walked a Windows admin through the process of setting up RAID during installation. It is remarkable complex and non-intuitive. In addition, the probability of a non-guru recovering from a disk failure with non-partitionable RAID is very low in my opinion: you have to repartition the disk manually and rebuild at least two RAID devices. Please reconsider. Having a RAID per partition is very clunky compared to RAID per disk. Or at least add a UI for recovery. Alternatively, if one could boot from LVM we wouldn't need this, but mdp is here and LVM boot is not.