I've seen a few tidy and well managed server rooms - and others better described as a disgrace with cables all over the place and through the doorway preventing closure, desks, open cabinets, additional electrical appliances, piles of papers and technical manuals on the floor, etc, etc. In my experience, IT people are probably some of the most untidy people around - second only to arts and entertainments staff. On the few occasions that I've been involved in the design of buildings with such rooms, 30min fire doors have been the norm.
Sliding doors have never been that popular with me. They're often installed because of lack of space for a normal door or to replace one - so inevitably you're looking at potential congestion and a door permanently wedged open, non-operational or off-track. Whilst OK 'in the text book' I prefer to plan for how people tend to use buildings. 'Playing safe' I suppose.