#59 properly supporting automatic degraded raid for unattended boot
Opened 2 years ago by chrismurphy. Modified 6 months ago

dracut currently handles this for mdadm, but no equivalent exists for Btrfs. It might only require some minor systemd and dracut work to support this for servers. But for desktops, it might also require kernel work to make btrfs more resilient.

https://github.com/dracutdevs/dracut/issues/1922


I would feel more comfortable if the kernel had some protection against the split brain scenario, e.g. "has been mounted degraded" flag possibly in the dev tree?

If present, only permit subsequent mount (degraded or not) when all the flagged degraded devices have the same transid.

The typical problem scenario is 2x device raid1, and each device is separately mounted degraded. In rare case transid of both devices could be the same, maybe it's enough to catch this by disallowing "all devices present have degraded flag set" because that's suspicious of the exact problem we want to avoid. At least one device must be non-degraded mounted, and should have a lower transid than the degraded mounted devices.

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