Let me clarify this a bit. We have a system with four identical drives configured with three slices--one for the OS, one for swap, and one for our application. We use gmirror to mirror the OS across all four drives. The third slice on each disk is not mirrored but is rather configured as a single file system and mounted for use by our our application.
When we take a drive out (assuming we're using the WD drives), the geom driver automatically detects the missing drive and takes it out of the mirror. If we put the drive back in, it is automatically re-inserted.
The problem is with the application slice. When a drive is removed and not properly unmounted first, attempting to force an unmount after the fact fails, and the system ends throwing a kernel panic.
We want to make an HA system that can handle the sudden loss of a drive, but so far we've been unable to get this to work with FreeBSD. Is there a solution?
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