Cable remediation in the data center

Cable remediation in the data center is a viable strategy for ameliorating inefficiencies caused by years of data center server add ons, moves and changes.

Many data centers today suffer from the moves, add-ons and changes that have been needed over the years. As businesses change, networks, servers and switches increase with need as opposed to planned expansion. This results in a marked increase in the number of cables under floors and in available pathways. In many instances there isn't room to add another cable due to the abandoned cables under the floor.

Remediate: Code, standards and performance concerns

Some countries, such as the United States in the new NEC 2005 (others likely to follow), require the removal of abandoned cable under the floor because it adds to the fuel/toxin load in the event of fire. This is particularly true of the older cables that did not have flame retardants in the cabling jackets. Code aside, data center managers often site unmanaged cabling as the number one concern. According to an IDC-MCS survey of over 300 data centers, the lack of well-managed cabling topped their list of top data center dangers. The effects of a non-structured cabling plant are certainly cumulative.

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Calculating costs of data center cabling infrastructure

To start, many data centers are faced with serious cooling inefficiencies necessitating that the cabling under the floor be addressed. A rat's nest of cabling can create an air dam through which no air can pass. If this happens to be in the airspace of equipment, the ambient temperature will rise and may cause failure. This is also true of a rat's nest in cabinets which have not traditionally provided the best pathways for cabling. Poor routing of cabling in a cabinet can block fans completely causing failures and of course, the resultant downtime.

Let's look at cable abatement. It may just be that the space is needed to upgrade the cable plant to support the new higher speed technologies like 10GBASE-T, Infiniband or 10GBASE-CX4, many of which use higher diameter cables which will exacerbate pathway issues. For instance the new pending category 6A UTP cabling has a maximum allowable diameter of .354" (compared to .250" for legacy category 6).

Category 6A F/UTP (also known as screened) is closer to legacy 6, but still slightly larger at .290", and in between is category 7/class (currently the only published standard for 10GBASE-T at a full 100m, the 6A standards will publish late this year or early next year) comes in at .330". All have a fixed horizontal MINIMUM of 15m which can either be taken up in pathways or with service loops which will increase pathway fill.

For Infiniband and 10GBASE-CX4, cable diameters are larger and in many cases are dependent on the manufacturer. Adding these to already overcrowded pathways or finding new pathways in areas where you don't want cable can wreak havoc in these environments. This can create a further necessity to remediate beyond strictly code issues.

In any case, remediation can seem like a daunting task. In some instances it may seem to make more sense to build a new data center, move and then remove the cabling (if required or to recuperate that investment through recycling efforts). In fact some installation companies are providing cable abatement programs at reduced rates due the high cost of copper and the ability to recycle the removed cable for a hefty profit. The cost of copper has tripled over the past few years and is now very profitable on the recycling market. Also, as some landlords realize that the code will require the removal of abandoned cable, they are making it mandatory that tenants remove their cabling when they vacate the premises.

To address many of these issues, TIA 942 is very specific in its direction to run horizontal and vertical cables to accommodate growth, which eliminates revisiting cabling, and its pathways and spaces. There are many reasons for this direction: those listed in the above paragraphs; the need to have networks documented and dressed for compliance and troubleshooting purposes; and the performance problems that can arise during MAC work.

Any time you revisit an area, you run the risk of harming what is already there. If the cabling plant becomes more susceptible to noise due to overfilled pathways which in effect flatten pairs, cabling being run too close to power, or even terminations that are damaged during MAC work, the performance of the network (found in bit errors) and the efficiencies of hardware due to increased need for DSP (digital signal processing to remove the noise) all compound to make for one big unhealthy mess. Add to that the need for compliance documentation, and you best bet is to install accommodating growth so that you don't complicate matters.

Moving to hot/cold aisle arrangements is a necessity for new equipment, which may escalate the need to remediate, move or consolidate to provide clear airways to provide the cold flow for the cold aisles. In particular if the static pressure and air space under the floor will not provide enough air flow to cool the newer, translated hotter, equipment due to the above or just poor choices in cable routing, remediation will become a must.

In making the decision whether to remediate, move or consolidate, we have looked at remediation and performance factors for an existing data center. Part two of this series will look at moving a data center and the best practices for the design of a higher performing data center. Part three will discuss the some considerations if you are moving to a collocation or hosted platform and the differences between the two.

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