SAP Servers Rack Best Practices -Data Center Rack and Stack

 Physical Installation:

• Racks must be physically positioned consistent with thermal/cooling requirements as published by the rack manufacturer (for example, many rack guidelines require 18″ clearance from walls, both front and rear). These guidelines are drawn up based on how the rack is physically constructed to cool down its contents – exhausting air from front to rear, bottom to top, or top to bottom.

 

• Racks should generally be purchased with the goal of maximizing available space. Thus, it’s usually recommended to go with the tallest rack (usually 42U, or 7 feet) capable of being housed by your data center. Other form factors are popular for less generous areas, including 36U and even diminutive 22U. Note that in many cases, it’s not necessarily the data center’s ceiling height that limits your choices; freight elevators and tight entrances more often impact your decision.

 

• Typically, between 6 and 9 racks are “grouped” in a row together. This centralizes and therefore minimizes power and network infrastructure in the sub-floors (standard cable trays can handle the typical number of server found in most racks today). It’s interesting to note that as server form factors shrink, this 6-to-9 rule of thumb may very well shrink to perhaps 4-to-6 in the very near future – be sure to consider the power, network, and KVM cable requirements for each server prior to physically placing/mounting your servers.

 

• Racks absolutely MUST be secured in a manner that does not allow them to tip forward, backward, or move from side to side. Following the 6-to-9 racks per group rule-of-thumb takes care of all of this, especially side-to-side movement. However, it’s both wise and advisable to secure even these groups of racks via “rack ballast” or similar kits.

 

• Between groups of racks, you must maintain a distance that allows the front door of one rack, and the back door of another, to be opened simultaneously. Of course, your specific thermal/cooling requirements may dictate even more space. Generally, this equates to about three standard 2×2 floor tiles. Keep in mind that different door styles (like “shutter style”) may minimize the physical space required; at the same time, deeper or “extended” racks are becoming more common, requiring additional front-to-rear space.

 

• Not surprisingly, heavy items should be placed lower in the racks, for both safety and center-of-balance considerations. This includes UPSes, large form-factor servers, and certain disk drive enclosures.

 

• Rack mountable keyboards should be placed in a manner that allows for comfortable access, based on the particular standing/sitting position or other arrangement in the data center.

 

• Consider the placement of SCSI-direct-attached tape drives carefully. The SCSI cables must reach the server(s), and the tape drives themselves must be accessible to allow for physically changing tapes and monitoring progress.

 

• Tape libraries should be located nearest to the servers that they will service, if cable lengths or constraints present a problem. Today, with fibre channel and switched fabric SANs, the cable length is not so much a problem as is basic cable management.

 

• Rack-mountable monitors should be placed in a position that minimizes neck strain, i.e. not in the uppermost rack position, or not too low in the rack. Alternatively, “local” monitors and keyboards may be foregone with the adoption of a good KVM solution.

 

Rack “blanking panels” must be employed where an empty space of greater than 1U exists. These ensure that air flow is not disturbed, and are therefore critical when it comes to cooling off the contents of a rack.