Have you thought about using Clonezilla and broadcasting out an image using PXE boot?

Would completely bypass the iSCSI setup, and each machine would still get the latest image from your server before the lan party begins.

A really neat thing about the netboot setup is it takes zero time to clone the image to all the machines. As soon as I'm done installing updates on one machine, I shut down, run one command that completes instantly, and now I can boot all the machines immediately with that image.

There have been a decent number of times when I actually did this during a party to fix an issue, or between parties just to keep the machines maintained for the family to play with, etc. It'd be hard to do that if I have to spend hours transferring a large image every time.

Aside from the stability issues at boot time, there isn't really a down side. I don't have any problems with load times. So I'm pretty happy with the setup.