Michael Petrino, Vice President of PTS Data Center Solutions (www.ptsdcs.com), says:

Air mixing – When air mixes between the hot and cold aisles this reduces the effective cooling of your CRAC systems. We implore that blanking panels be utilized in all open “U” locations inside of an IT rack and areas where there is an empty spot in the row of racks we add clear plastic air blocking material to create a barrier between the hot and cold aisle.

Where to deploy new servers, especially blades and virtualized machines – We recommend having a CFD baseline of your data center done by a consultant. Once you have an accurate model it is possible to have scenarios run to decide where the best and safest location in the room exists to add heat load. New devices can be modeled in your existing space reducing the occurrence of hot spots and the need for having to rerun cable or fiber to a different location when you deploy incorrectly. By doing the planning up front you deploy more accurately with predictable results and improved performance. Very often we come across high density machines deployed in a legacy data center followed by box fans in the hot aisle to reduce and move the heat, this is not a planned and reliable approach.