Howtoforge posted a tutorial about using iSCSI on Debian Squeeze

This guide explains how you can set up an iSCSI target and an iSCSI initiator (client), both running Debian Squeeze. The iSCSI protocol is a storage area network (SAN) protocol which allows iSCSI initiators to use storage devices on the (remote) iSCSI target using normal ethernet cabling. To the iSCSI initiator, the remote storage looks like a normal, locally-attached hard drive.

  Using iSCSI On Debian Squeeze (Initiator And Target)