Raised floor cooling can provide an efficient and flexible environment within which datacenter operations can occur. However, over time, changes to the setup of the floor (both above and underfloor) accumulate and can result in less and less efficiency over time.
Perforated tiles are a case in point. They provide great flexibility – if a particular rack or row is not getting enough cold air into equipment intakes, it’s easy enough to replace a floor tile with a perforated one, bringing cold air directly into the problem area.
However, if floor tile management is not incorporated into the data center’s move/add/change process, major local disconnects between the supply environment and the equipment demand can arise.
SynapSense has seen a number of different issues regarding perforated tile management in datacenters, including:
1.) Perforated tiles located in areas no longer serving active equipment.
This is the natural result of any Move/Add/Change process that does not include floor tile adjustment as part of its checklist of procedures to follow.
2.) High-flow perforated tiles placed where standard perforated tiles are sufficient.
This, too, is a natural result of the Move/Add/Change process; however, is more often due to trying to fix a hot-spot without fully understanding the reason the hot-spot is there.
3.) Perforated tiles absent in areas with hotspots.
This can result from simply failing to instrument the data center for temperature monitoring – taking ones eye off the ball, so to speak.
4.) Missing perforated tiles.
These are actual INTENTIONALLY CREATED HOLES IN YOUR DATACENTER FLOOR. To some this may sound incredible, but it’s human nature that if there is a problem, one tries to take care of it. If there is a hotspot, and no perforated tiles are available in inventory, it may seem natural, in the heat of the moment (so to speak ;-), to simply remove the existing tile and planning on ordering a new perforated tile to replace it later. However, the dangers of leaving an open hole in a raised floor, (dangers to both humans and equipment alike) should be obvious. Holes in a data center floor are, flatly, unacceptable, period.
4.) Perforated tiles partially, or even wholly, under static equipment racks.
Sometimes we see perforated tiles where half of the tile is underneath a rack, allowing cold air to be blown up and hit the bottom piece of equipment. The problem with this is the air will often recirculate under the rack into the hot aisle, violating hot aisle/cold aisle containment and reducing efficiency.
5.) Perforated tiles in hot aisles.
This causes mixing of hot exhaust air from IT equipment and cold intake air from under the floor and reduces efficiency.
6.) Damaged perforated tiles.
Even a small chip can significantly reduce the structural integrity of a tile. Since even a perforated tile is load-bearing (humans walk on them, fully loaded racks are wheeled around over them, and so on), any damaged tiles should be replaced.
7.) Holistic Issues Stemming from Individual Changes
The most common problem that SynapSense has seen in data centers with perforated tiles stems from a problem similar to the “Tragedy of the Commons”. This refers to feudal England in former times, when villagers would allow their cattle and other animals to graze on common ground. Individually this was not a problem, but since there was no feedback loop discouraging use, individuals tended to have their animals overgraze more than their fair share – and if everyone does this, the entire system collapses.
With perforated tiles, it’s much the same – they provide wonderful flexibility, and the ability to make a change to a datacenter without having to go “back to the drawing board” by simply swapping tiles is a huge advantage. However, remove enough solid tiles in aggregate – whether for the entire data center, or a zone – and there are larger implications. Overall underfloor static pressure drops with each solid tile removed, requiring other steps to increase that pressure – perhaps employing one or more additional CRACs, increasing fan speeds and so on – and reducing overall efficiency. Monitoring the sub-floor pressure and server inlet temperature is a great way to keep the cold air supply in balance and directed to the locations it is needed.
The data center floor environment needs to be examined from a holistic perspective – ideally on a regular or even continuous basis – so these aggregate problems that stem from individual actions can be identified.
Perforated tiles may not look like the most exciting weapon in a data center manager’s quiver, but properly wielded, they can solve short-term problems very effectively. The trick is not to use them in a way that contributes to larger issues.