I have a 3U server colocated in 4U of space (the smallest in the facility I'm in.) I'm thinking of adding a second 1U server. I'll run Apache, QMail, DJBDNS on the new machine and MySQL on the older machine. My thought is to just run my single ethernet drop into 1 NIC on the new machine, and then connect the old server to the 2nd NIC on the new machine. Does that make sense? Is there any reason I might want to buy a switch and connect both machines to it? Thanks for any thoughts.
That should work fine, as long as you are not concerned about making one of the servers a single point of failure. Depending on whether one of your NICs supports auto-MDIX, you may need to use a crossover cable rather than a regular ethernet cable.