Random Raw Device names issue on RHEL 3.0

[umeryounis]

Dear All,
I am facing issue regarding raw devices names.When i present ist device from EVA to my host server;OS allocates it the name of /dev/sda. when i present 2nd device from EVA on same device ;OS allocates it a random name of /dev/sdc. i checked on same server that whether /dev/sdb is busy or not . but i found that /dev/sdb is not busy but OS didnt alloacte it. Similarly, on further disk presentation on same server, OS alloactes random device names and on every new entry of disk, OS modifies previous device name entries as well (e.g.)it changes device name /dev/sdc to /dev/sdw....
Pls help me in identifying the issue and suggest a solution accordingly...
Thanking you all in anticipation...