50 meters should be doable with copper, but at that distance I'd suggest to start considering optical cables. Will there be (iSCSI) switches in both server rooms? If so you could do copper (cheaper cables) and get an IO module for each side with optical ports to link the 2 rooms together.
I am looking to purchase two Compellent SAN's and wondered if anyone had a preference for fiber or copper for connectivity.  The SAN's will primarily be used for Vmware and also SQL data.  Some of my hosts already have 10gb NIC's so using copper would mean I wouldn't have to purchase so many HBA's, but that is the only think swinging the decision at the moment.  I have read that you will see more latency over a copper connection than a fiber.  Any thoughts would be appreciated.
Fiber or copper?