Monday, May 7, 2007

i’m in ur RAID, striping ur disks all the way to CA

Recently I acquired a pair of 500GB USB2 hard disks that I use in a RAID-1 configuration (on two different host controllers!); you know, to store my photos and other important, uh, stuff. I had some spare time this weekend to look at fd.o #6426 so I wrote a small patch to teach HAL about Linux software RAID.

gnome-device-manager showing Software RAID drive
RAID rebuilding

I also whipped up patch to gnome-device-manager such as to show the new properties introduced including whether an array is running in degraded mode or is being rebuilt. It’s pretty spiffy.

All that this code is doing right now is basically just listening to kernel events (via udev and priority data on /proc/mdstat) and then representing the RAID arrays as HAL drives and volumes. It’s spiffy because the RAID drive inherits things like storage.hotpluggable from the physical components (e.g. the two USB hard disks) so in my case the RAID array simply appears in Nautilus and is totally mountable just like a regular external drive. Works out of the box. Desktop integration++. However, we can do a bit better so for GNOME 2.20 I’ll be writing some patches to gnome-vfs and gvfs. You know, to use the new HAL properties to choose some helpful icons and icon captions.

Going forward, there needs to be some way of assembling and disassembling RAID arrays; hot-adding components to degraded arrays and so on and so on. Probably neither Nautilus nor gnome-device-manager is the right approach here. And there will probably be some sort of auto-assembly happening at the system-wide level anyway, need to sort that out with Kay (the udev maintainer) and also talk to various distro maintainers too. It’s also probably also time to revive my never properly announced GNOME Disk Utility project. Actually, that’s one reason that I split the Device Manager into a shell and library component; right now the shell is around 1200 lines (compared to 4000+ for the library) and there’s no reason that the Disk Utility shell would be a lot bigger. Plus it’s always awesome to put pretty UI on top of useful infrastructure.

Tomorrow I’m leaving for The Golden State to go the Red Hat summit, then hang out with Kay Sievers and finish off the west-coast invasion with FreedomHEC. The next two weeks are going to be busy.