We have a few zones that live on an iSCSI NetApp LUN.
So far, we only use this on test/dev environments, because we found that there are some issues with Solaris iSCSI timeouts. E.g. at boot time, the iSCSI timeout is exactly zero seconds, zero retries. So if the first attempt to mount the LUN fails, your Solaris box goes into maintenance mode and just sits there until somebody looks at it.
What would be great is running Solaris zones over NFS instead of iSCSI (like VMWare NFS datastores). Gives you all the NetApp advantages and the extra reliability and robustness of NFS, and none of the management complexity of iSCSI LUNs.
Further to what Karl said, we found that once we had more than four iSCSI LUNs on a Solaris server running Zones, we would start getting a lot of time-outs and eventually several of the LUNs would get dropped. iSCSI doesn't seem to work well for this.
I would like to see this done over NFS if Sun can't improve their iSCSI client.