by September 5, 2008 0 comments



Racks and enclosures form an important aspect of data center management. To
add to the overall efficiency of your data center you need to maintain a
congenial environment for servers, storage boxes, network switches, etc.

Thinking of racks and enclosures as just dumb shelves is a huge mistake no IT
manager should make. However, buying racks and the right accessories for your
data center is not an easy task. Lots of engineering goes behind maintaining and
designing your datacenter. All IT equipment needs to be well connected to the
data center’s network. This is what calls for custom racks that best suit your
needs. Your racks must have sufficient cooling fans and air distribution units
to dissipate heat and be equipped with enough power distribution units to power
all equipment inside. Proper cable management is equally important. You need to
choose the right kind of enclosures as frequent assembling & disassembling can
be a sheer nightmare for IT managers. Let’s get into more detail of what you
need to keep in mind before buying racks for your data centers.

Analyze your requirements
You need to consider several aspects before buying racks and enclosures.
Racks and equipment that go into it should be standards compliant, so you should
first get the dimensions of all your equipment. Racks are a long-term
investments so you have to carry the capacity planning for your datacenter
keeping in mind your future procurements plan. Besides, requirements for
accessories keep increasing, so you should ensure that you are not short of
space in your racks in near the future.

Pricing
Incidentally, every single accessory that you add to your rack will cost
you. So, before you go and ask for a quote of racks, it’s better to do your
homework well, to avoid getting fooled by the vendor. You obviously don’t want
to end up with unwanted accessories imposed upon you. There are plenty of sites
that will tell you about the kind of accessories available for racks.

Size and dimensions
The size of racks depends on how much equipment you plan to purchase and the
floor space available in your data center. How the size of a rack is measured?
The standard measurement of a rack is done in terms of rack units, where 1 rack
unit (also known as 1U) is 1.75 inches tall. There are multi U racks available
in the market, such as 42U, 45U, 48U etc. This means, in a single 42U rack, 42
servers or other electronic equipment of 1U height each can be stacked up. And
of course, there are lots of equipment that are of 2U and 4U size.

A standard which is used to define different features of racks such as, rack
unit, vertical and horizontal hole spacing, rack opening width etc. This has
been defined by EIA (Electronics Industries Association). Unfortunately, this
standard fails to define each and every detail of a rack. Therefore even when
you buy a rack that follows these standards, chances of your server or other
electronic equipment not fitting in still exist. For instance it doesn’t define
whether a rack should have two or four posts, how deep should it be, whether the
rack holes are square or round (though square holes are most common these days),
the distance between the two front posts etc. Another interesting fact is, the
most commonly available 19 inch racks can’t accommodate servers of the same
width.

Rack types
Three types of racks are available today: 4 post, 2 post and wall mountable.
The nomenclature behind them is simple. A 4 post rack has four upright angles to
hold all the equipment and likewise, 2 posts have two such uprights. Further
classification of a 4 post rack can be into an open frame or a closed frame
rack. An open frame rack doesn’t have any side panels, or front and rear doors.
The one that does have these is a closed frame. Open frame racks are cheaper
because of less use of metal. But one disadvantage of closed frame is restricted
access to cabling due to an enclosed design.

The 2 post racks generally don’t have any panels. They are cheaper, but look
more cluttered. These can generally be used where space is at a premium. Most of
these racks find use where either the requirement is only of two to three racks
or in huge data centers where space utilization and cooling becomes a priority.
Usually racks are made of aluminum extrusion which gives it strength and lighter
weight with threaded holes on them. There are also transportable, wall
mountable, and portable racks. All these are smaller and can be moved around
easily.

Heating issues
What forms an important part of a rack is airflow. There are different
technologies used for airflow inside a rack. You should check if the cooler air
is able to reach the equipment inside the racks. There are also rack doors with
perforation.

Racks of glass doors use alternative methods of cooling. The air is not let
freely in and out of the data center, but pushed through the rack, from the
raised floors.

There are also special air distribution units attached at the bottom of the
rack, which would suck in air from the raised floor.

For cooling racks, enclosure blowers and fan systems are another solution.
Here blowers and fans are installed inside the racks for efficient removal of
heat.Using the surrounding cooler air, these blowers and fans get rid of the
heat generated inside.

Optimally placing these equipment inside the rack is essential for maximum
performance.

Cooling in high density racks
Unless you want your data center to turn into an electric furnace for your
equipment, cooling remains an important issue to keep in mind. Many high density
equipment are available these days for data center.

For example, Blade servers generate a lot of heat because they are all packed
so closely together. For this you would require a special air removal unit or a
roof fan tray in case you want proper exit for the hot air inside racks.

Like in nuclear reactors and power plants, special liquid cooling packages
are also available for racks. These packages are intelligently built for optimum
use of power supply, i.e. water flow and fan speed can be controlled according
to the heat generated. One can also use chillers for effective cooling of racks.
These come in variable sizes and mostly have removable panels for easy access
for servicing.

Equipping racks with temperature and humidity sensors and controllers can
also prove to be very efficient. These sensors can further be connected to your
data center network, thus allowing you to monitor and control the temperature
and humidity in a data center.

Cable management
While setting up a new rack, cabling should carefully be taken care of. As
data center people have to move equipment around, in a data center to
troubleshoot faults etc. the cabling generally becomes a complete mess. Hence, a
rack which is designed to help manage cabling would be a good choice. The
cabling in racks can come through the raised floor or from the ceilings. In any
case, racks should have proper guides to ensure proper cable management.

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