My HP-N36L-NAS not only serves as a data storage for photos, but also as a storage location for virtual disk images used by VirtualBox: there is simply not enough space on my surf and work PC thanks to SSD. Since the configuration of iSCSI is already described in the FreeNAS Wiki, here are just a few performance data of my setup:
It is achieved with four Hitachi 2-terabyte hard disks with 5,400rpm, which are configured with ZFS as RAIDZ. Furthermore, 8 gigabytes of RAM are installed to give the ZFS enough space to work. For ISCSI 100 GB are reserved, enough for my purposes. So Ubuntu 12.04 LTS can be used in a virtual machine without any problems. The boot time might not be as good as native on a fast system, but it is quite sufficient. The SSD in the host computer reaches of course still clearly other performance regions.