Hi, Cougar. Welcome to the forums. The answers really depend on what type of equipment you expect to deploy. We just finished remodeling a small, traditionally (subfloor) cooled, general purpose data center. Today we're mostly using 1U and 2U servers and disk arrays, but we anticipate more blades and other higher density form factors sooner or later. Here's what I think:
- Rack Depth: 1200 mm (48") - Allows increased equipment depth and in-rack cabling space
- Cold Aisle Width: 1800 mm (72") - Increases air supply by 50% vs. 1200 mm aisles
- Hot Aisle Width: 1200 mm - Provides adequate rear rack service area, aligns racks with floor grid to optimize subfloor access
Overall, since anticipating the future is an inexact science, expect to be wrong on some dimension -- space, power, cooling, cableway, floor loading, etc. Be sure to have a plan for 1) providing more of that resource when you run out, or 2) how to avoid running out.
I hope others will chime in with their views.
Ken