Friday, August 13, 2010

How much data center space do you need?

With the explosion of hypervisor and virtual technology you can consolidate most of your server infrastructure down to a few host servers. Instead of having one physical server running on one server machine with enough resources (CPU, RAM, network and storage) you can run several virtual servers on one physical server machine. Today’s modern servers can hold several CPU’s and hundreds of Gigabytes of ram which allows you to pool and divide resources. It is not uncommon for organizations to consolidate twenty or more physical servers down to 20 virtual servers running on one power full host machine.
You will require less data center space but your host servers running all the virtual serves tend to use more power than servers from just a few years ago. You probably will not be able to fill a full 42U with equipment as the power density will be too high. Data centers have an 80% rule for power. If you order a 20 amp circuit you can only use 16 amps because you will need headroom for the equipment to power on. Modern servers fully loaded with drives CPU’s and RAM can consume 1.5 to 3.5 amps of power. Plus you will have other equipment in the cabinet like switches and firewalls. Some firewalls now will run as a virtual machine and eliminates the need for addition power and space in the cabinet.
Most data centers depending on their infrastructure will allow 40 amps 110 power or 20 amps of 208. With today’s equipment power density you will probably never be able to fill a rack with equipment the heat and power draw will be too much. Most data centers have a one cabinet minimum, a few data centers do offer locking half cabinets but this is not common and you will have to check with the facilities.
If you only need a server or two collocated the best option is to find the best data center facilities in your area or region. Look for computer and consulting companies that operate out of those facilities. A lot of smaller computer and consulting companies will offer shared colocation space. Your server will be in a locking cabinet with other customers. The advantages of doing this are that you only pay for the space you need. This is a great option to start out. The pricing per U will vary from data center to data center. Quality carrier class facilities start at around $80 per U. Modern redundant facilities may be more up to $175 per U. The disadvantages are security and easy access to your server. With so much running on one physical server you want to order your server with dual power supplies. If possible you will want to plug into separate PDU’s (power distribution units). Better PDU’s will let you meter your power and remote reboot the server if needed. This will save you from having to go to the data center or have data center personal walk out to your server and have to manually push the power button.
When you order your server get a remote access card. This allows you console access to your server even if it is hung on a screen. You will be able to see error messages or even do maintenance and installations. This does cost extra but will save you downtime and allow you to come quickly or recover from disaster.
Make sure you pick a data center with multiple carriers or ISP’s. I suggest a minimum of three or more. You will also want to have redundant cross connects to your switch or server. This way you will not be down due to accidents or facility maintenance.
The most important consideration when picking your facilities is how much redundancy they have and how much redundancy you have built into your server.

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