"sharing" hot spares?

[Charles Sprickman]

All,

This is probably an odd question...  We're extensively using ZFS on a 
bunch of 1U boxes and packing all the drive bays full.  This is all SATA, 
so I would like to have hot spares available, but without migrating 
everything to new enclosures, I'm not seeing an easy way to deal with 
this.

Is there anything out there that would allow me to export a few drives 
from another box as block devices that the other boxes could *temporarily* 
use as hot spares until someone onsite could physically do a drive swap?

I would also really like to share one drive amongst multiple hosts - I am 
making the likely over-optimistic assumption that I'll be dealing with no 
more than one drive failure per say, 3 hosts at a time.

-hast doesn't seem quite right, as it's more about clustering than just 
exporting a device.

-geom-gate looks like it might fill the bill, but I'm unsure as to whether 
it would allow an export of one drive to more than one box, and if it did, 
if it would have any way of letting a second host know the drive is busy.

-iscsi seems like it might work as well, but I'm leery of anything not 
deemed stable/supported enough to be in the base system.

Anything else?

I'm also totally clueless as to how zfs would deal with having one drive 
coming over the network while the others are local.  I assume it should 
work.

Also if there was a reboot while it was running with a disk from this 
network spare "pool", could zfs then find the network drive it was using 
since it will be available later than the local drives?

This whole scheme is just something that came to me a few minutes ago, my 
apologies if it sounds a bit nuts.  Just trying to solve an interesting 
problem.

Thanks,

Charles