Comment 6 for bug 259145

Revision history for this message
ceg (ceg) wrote :

Raid systems introduce redundancy to be able to keep working even if parts of the system fail.

I think the init.d/mdadm scripts (early/late or simillar) that debian uses to assemble and run degraded arrays on boot have been removed because all arrays are set up using udev. But we don't have any replacement functionality to run degraded non-root arrays on boot.

If we fail and drop to a recovery console on boot, the system isn't really failure tolerant.

Auto-running *only selected* arrays if they are found degraded on boot probably requires a watchlist:

* For each filesystem mentioned in fstab that depends on a an array, the watchlist file needs to describe its dependency tree of raid devices. The file needs to be (auto)recreated during update-initramfs.

    * initramfs should only watch out for and run rootfs dependencies if necessary.

    * later at boot mountall watches for and runs other (bootwait) filesystems mentioned in the watchlist.
          * Is there a way to nicely auto-update the raid dependency trees of non-rootfs in the watch list upon changes?
                * The file could be updated/validated on every shutdown.

For more context look for MD_COMPLETION_WAIT and "How would you decide what devices are needed?" at https://wiki.ubuntu.com/ReliableRaid