The Pro series of NAS from ReadyNAS (Netgear) support iSCSI out of the box. But the NV+ 4disk unit does not. However - a third party plugin is available.

Target

The provides support for the iSCSI target on the NAS itself.

There is a fairly good guide available on the wiki at readynasfreeware.

In short - it's:

Upload the bin for the plugin
Place a config file on the unit (root ssh required)
Create a file (it also supports partitions etc) to contain the disk image
Add startup/shutdown links
Start the service.

I followed the wiki with only a couple of changes.

In the ietd.conf file - the line:

Target iqn.2001-04.com.example:readyduo.iscsi.target0

The format is iqn.YYYY-mm.tld.reverse.domain.name:descriptive.string.

The dd command (I created a 500Gb file) took 5 hours - don't do this if you're in a hurry ;)

And at the end - when it asks you to start I kept getting "failed". Turns out the install starts it unconfigured. All I had to do was a

/etc/init.d/rfw-iscsi-target stop

before running the start.

Initiator

For a client to connect to an iSCSI target it needs an initiator.

ReadyNAS has a page that shows how to install and configure globalSAN's free iSCSI initiator. It will require a restart of the mac. I grabbed the beta as it said it supported snow leopard. It has a few changes in layout - but the process is the same:

Add Portal pointing at the NAS
Add a target from the list on that portal.

I was then able to format the newly initiated drive and mount it read/write.

Speed tests

For this - I copied a 192Mb file back and forward. These are just for fun - highly unscientific - nothing done to check for caching etc, or other busy devices on the network.

Conclusion

Well it works - but it's not a world speed revolution ;)