Posted by Kim Otte on Wed, Jun 02, 2010 @ 09:33 AM
Building a new data center or server room is a very complex project, whether you're building a small 1,000-square-foot server room or a 100,000-square-foot data center. Here are some important facts your IT department needs to think about prior to beginning:
- Determine design requirements early in the process:
- IT hardware load projections and cabinet load densities (blade servers?).
- Electrical and HVAC redundancy options.
- Fire detection and suppression systems options.
- Site selection:
- Square foot requirement.
- Structural requirements (ground floor or upper floor loading issues).
- Proximity to utilities (power, cooling, communication).
- Comprehensive, coordinated design documents ensure a successful construction project:
- Partner with a data center consultant with specific experience in this industry.
- A design consultant with data center construction and service experience will incorporate maintainability into the design.
- Engineering site reviews during construction ensure that the design criteria are incorporated into the build-out.
- Properly document warranty and service agreements:
- Part of the construction project close-out should include warranty documentation.
- Warranties typically carry some level of parts replacement, but do not include preventive maintenance agreements.
- Service and maintenance agreements during and after the warranty period should be planned and can be budgeted at the close of the construction project.
These are just a few critical things that need to be looked at during the construction of your data center - if you don't have staff with the skill set to manage this process, it is extremely important that you hire a construction company who focuses on building data centers or to hire a data center consultant to represent them during the construction.
Submitted by Jim Stark, Design/Build Manager - Electronic Environments Corporation
Posted by Kim Otte on Mon, Feb 01, 2010 @ 02:50 PM
Submitted by Wally Phelps - Engineering Manager with AdaptivCool, an EEC partner
Blade servers and other high density IT equipment is becoming more mainstream by the day. Data Centers and server rooms that were designed to cool 1-3KW racks are now being asked to house and cool racks of 10KW or more. Computer Room Air Conditioning (CRAC) capacity is often more than adequate, however distributing the additional cooling air required pushes sited and the new IT gear to the breaking point.
The root cause is twofold. On the supply side there is often not enough static pressure under the floor to allow even open grate style perforated tiles to flow enough air. Typical data center design is target
ed at 0.1"wc of static pressure. Actual measurements on hundreds of existing data centers shows typical pressures of 0.02 to 0.05" wc; less than half of the design point. The causes of this low pressure are myriad, from unintended breaches in walls and support columns that go un-noticed to excess cable cutouts and simply too many perforated tiles. Underfloor obstructions also prevent static pressure from being evenly distributed as does CRAC placement that causes underfloor vortexes and low pressure from colliding air streams under floor.
On the return side, the hot air exhaust from these new high density servers must have an unimpeded low resistance path back to the CRACs; to be cooled and reprocessed. High density equipment ejects a much higher volume of warmer air than many data centers can cope with; causing other servers in the room to literally choke on the hot exhaust of its neighbors.
The solutions can often be relatively simple, such as blocking cable cutouts that waste precious cold air, adding blanking panels or moving racks to more ideal locations (when possible). Even with these measures however static pressure tends to still be much lower than design. A typical improvement in static pressure from closing cable cutouts is 20% which equates to static pressures of 0.03" to 0.06", still far below design point and not able to cope with high density racks.
A more effective solution that immediately solves poor cooling distribution is to use active airflow devices. These can be thermostaticall
y controlled underfloor air movers that install quickly and unobtrusively under existing perforated tiles. These devices deliver up to 1200 CFM to supply racks of 10-12KW with more than adequate cooling air. Even at very low static pressures! Another solution is overhead return air movers that pull hot exhaust air up and away from neighboring racks and deliver it efficiently to CRAC intakes.
The solution for cooling high density IT equipment is simple. Provide enough cool air to the intake side and ensure the hot exhaust does not affect other racks.
Posted by Kim Otte on Tue, Dec 08, 2009 @ 12:06 PM
The size and shape of a data center can impact the ability of Computer Room Air Conditioning (CRAC) systems to adequately cool the heat loads. Larger rooms will typically require a greater number of CRAC units due to limitations on air delivery of the units. So, although a single unit may have the BTU (British thermal unit) capacity to cool a given load, it may be unable to effectively deliver the cool air if the load is spread out in a large room.
Odd shapes and obstructions also present air delivery problems and can be especially problematic when trying to achieve redundancy of CRAC units. These limitations apply mostly to traditional CRAC units which deliver air through a raised-floor plenum or overhead ductwork. In-row cooling solutions can overcome some of these limitations since the units are placed close to the heat load, and redundant units can be placed in the rows, as well. Raised-floor applications with traditional CRAC units, fan-tray supply diffusers and return-air fan products can improve air delivery, redundancy, and efficiency.
Data centers or server rooms with alcoves, L shapes, or two large rooms connected in a disjointed fashion also create problems. Consistently, we find these are really two separate environments with little in common when it comes to airflow and cooling. In cases where moderate-density equipment has been placed in an alcove or other similarly obscured part of the room, some type of assisted or active airflow is usually necessary to move cooling in, move heat out, or both.
Ceiling Height 
Whether ceiling height affects cooling largely depends on how well the room is laid out. If there is a proper hot aisle/cold aisle layout with CRACs placed at the ends of the rows with at least 36-inch wide hot aisles and 48-inch wide cold aisles, a ceiling as short as 8 feet can work. It's difficult at 8 feet to use overhead cable trays, however, so a 9-feet minimum is recommended to keep data cables out of the raised floor.
If the room does not have a proper hot aisle/cold aisle layout, then more ceiling height will help promote a lower resistance path to the CRAC returns. In this case, higher ceiling heights can also be used to promote a stratification layer where hot air collects at the top. The CRAC returns can be raised up to at least 2 feet below the ceiling to collect the hottest possible air. If there is a suboptimal layout and a low ceiling, then active airflow devices can come into play to force the air away from its "lazy path" and direct it to racks or CRACs as needed.
Gauging a Room's Coolability
There are many factors to gauging a server room's coolability, but they all come down to how efficiently the right amount of cooling can be delivered from the cooling units to the rack intakes, and then how efficiently the warm air can make its way back to the cooling unit returns. The enemy at all times is the mixing of hot and cold air.
The following factors should be considered when determining a data center's coolability:
- CRAC orientation. The CRACs should be at the ends of the rows to allow cooling and heat to flow easily in and out of the rows with the minimum amount of mixing.
- Raised floor height. As a general rule, a 10,000-square-foot data center should have a minimum of 2 feet. Smaller sites can get by with less; larger sites need more.
- Underfloor obstructions. Obstructions close to CRAC units cause the most problems. As you get farther away from the CRACs, they become less intrusive. Cable trays and other large obstructions should be limited to the hot aisles if possible.
- Shape. Square or rectangular rooms will usually be easier to cool.
Floor cutouts. These should be small enough so that excess air is not leaking out to spaces that don't need cooling, if you do have them you should be using brush sealed raised floor grommets to control the leaking.
- Ceiling height. It is often difficult to get good return air paths below 9 feet.
- Ducted ceiling returns or containment. These always improve the coolability of a data center when properly engineered. Special attention must be paid to local fire code enforcement, which varies widely.
- Blanking panels. These prevent recirculation of hot air from the back to front of a rack. If there is not enough CFM (cubic feet per minute) being delivered to the front of the racks, blanking panels won't help.
What shape is your data center or server room? Have you already put some of these best practices to work and if so, have you seen better cooling in your data center?