I was thinking of creating a HAST disk and using that as second
disk to a VM. It seems that when the backing file is gone and
returned, it's never re-opened. Is this scenario possible?

Host machine:
root@moby:~/VMs # diskinfo /dev/hast/shared
/dev/hast/shared        512     21474830848     41943029        0       0

and from withing the VM:
root@lamb:~ # diskinfo /dev/vtbd2
/dev/vtbd2      512     21474830848     41943029        0       0
root@lamb:~ # file -s /dev/vtbd2
/dev/vtbd2: Unix Fast File system [v2] (little-endian) last mounted on /mnt, 
last written at Sat Aug  1 19:33:17 2015, clean flag 0, readonly flag 0, number 
of blocks 5242878, number of data blocks 5076797, number of cylinder groups 33, 
block size 32768, fragment size 4096, average file size 16384, average number 
of files in dir 64, pending blocks to free 0, pending inodes to free 0, 
system-wide uuid 0, minimum percentage of free blocks 8, TIME optimization

Then I go to the host, destroy /dev/hast/shared and re-create it.
The VM is not able to use the disk anymore:
root@lamb:~ # file -s /dev/vtbd2
vtbd2: hard error cmd=read 0-255
/dev/vtbd2: ERROR: cannot read `/dev/vtbd2' (Input/output error)

Is this possible? Can I somehow achieve hot-plugging a disk?

Thanks for any thoughts,
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