Firewire Drive Enclosures

I need more storage for video editing, I would like to get a multi bay firewire enclosure and I have a few questions regarding them:

• Does anyone know where I can get a 2U or 3U rack mounted enclosure?
• If I get a four drive [two board Master/slave] vs. a four board [master/master] what is the performance difference?
• Do all four drives have to be the same size?
• Are they hot swappable?
• I believe FW800 is an 9pin and FW400 is six, can you plug a FW800 enclosure into a FW400 firewire card?
• In a four drive enclosure with two boards do you have 2 firewire cables [1each] running to the computer?
• Is it possible [easy] to build a rack mounted firewire drive enclosure?

If anyone has any suggestions on where I can purchase these things would be greatly appreciated.

Thanks.