In this article, we're going to look configuring access to an iSCSI server from Mac OS X. In particular, this will be useful for Time Machine backups; this is what I do at home for my macs.

In the early days of the Internet data links were slow and lots of traffic was based on single character transactions. For example, the telnet protocol sends a single byte at a time as you type. This isn't great use of the available bandwidth as the overhead of delivery is very large. An IP header is (a minimum of) 20 bytes and a TCP header is another 20 bytes. That means that to deliver one byte of data, cost a minimum of 40 bytes. That's 40:1. Not good. To make this worse, each packet will require an ACK packet to come back from the other end of the connection.

FreeBSD 8.0 doesn't natively support an iSCSI target server. This was a bit of a surprise when I discovered this fact, but I was sure that the ports database would include something that I could use. This technote shows how to set up the target server I found and have working. I'm running VM's on it from my ESXi servers and performance seems pretty good. (Especially considering that the FreeBSD installation in question is also a virtual machine, but that is another story...)

The iSCSI target server that I'm using is the istgt daemon. To compile and install this is simplicity itself.