ISCSI on zvols with two maschines. What needs to be done?

[dennis berger]

Hi folks,

The following question often comes to me, when I speak to my customers.

Is it possible to attach two systems to the same storage array using shared SAS and use istgt + zfs to provide 
a reliable ISCSI target. This could be active/passive or later active/active. In case it's not possible, what needs to be done?

The questions that came into my mind.

Can I connect two freebsd to the storage and boot them up? Just that both systems would see the physical devices. 
Can I start ZFS on both systems without writing on it? I would like to use just block devices for ISCSI. Is everything still consistent?
Does starting ZFS up already writing some sort of meta data to the physical devices?!
Can I start istgt on both systems without actually using the istgt on one system?! Then CARP would be enough, wouldn't it.

Or in case of active/active extend istgt to communicate with the other istgt to not hand out a device twice? 


Best,
-dennis