Data Center Selection Criteria :: Changing web host
Data Center Selection Criteria
There are two broad categories of data center providers. The first only supply computer room floor space, access to an ISP, basic monitoring and power. These are called collocation providers. The second group provides more comprehensive management that may include all possible IT services related to your site including systems development. These are called managed hosting providers. There are a wide range of varying service levels in between and the interpretation of the terms within the industry can often be very loose. Always request a very specific list of the services your data center provides as part of your selection process.
As expected, the selection of a suitable data center will play an important role in any data center or web farm relocation project. There are many factors related to the facility and its services that need to be considered that are often overlooked. These include:
The data center should be positioned away from zones at risk from natural disasters such as flooding from rivers and dams, hurricanes and earthquakes. It should also be no closer than a quarter kilometer away from major highways and railroads to reduce the evacuation risk from toxic spills. Locations close to hazardous production facilities and aircraft flight corridors should be avoided.
Your employees may have other personal interests in the location such as the presence of reasonably priced housing nearby, recreational attractions in the area, access to public transportation, and the availability of amenities such as schools and parks in the neighborhood. You should monitor how traffic patterns affect the ease of accessibility to the site to see whether they are unsuitable.
The immediate vicinity of the site is also important. Rainwater should drain away from the building and then off site to prevent localized flooding. In high security environments the building should be surrounded by embankments and perimeter fencing, reducing the risk physical attack.
The facility should have access to multiple ISPs with the cable entering from different points of the building. This reduces the risk of outages due to a technical failures as well as construction and landscaping accidents. Verify the roof access rights in the event you need to have a satellite or microwave line of sight antenna installed.
Power should be supplied from multiple feeds from different substations. The facility should also be able to run without interruption if its largest standby generator or UPS are offline for maintenance. Ensure that the building has sufficient excess capacity to handle future growth.
In large facilities the UPS feeds a network of power distribution units (PDUs) to supply each section of the floor with a series of circuit breaker panels. Make sure that every rack or cabinet you intend to use has access to outlets from at least two PDUs and that each PDU is operating at no more than 45% so that it can handle the full load of the other one if it fails.
Request a history of outages or other irregularities in the feeds from the sites utilities and ask how youll be notified by the facility of any electrical maintenance work to be carried out by either themselves or their providers. The facilitys staff should also be automatically notified by monitoring equipment of any disruptions in the power supply to the area.
Ask how quickly the generators respond to an electrical outage and how long the UPS batteries can last. Inquire about whether the UPSs have ever supplied the full load of the data center and when last the system, including the batteries, was last maintained. Standby generators can be regularly started without revealing any apparent problems, ask whether testing includes the use of a load bank to simulate the power consumption of the data center. Investigate how frequently the equipment is tested and how often it is maintained.
Most data centers try to maintain a 75F/25C air temperature, verify this. On your plant tour be on the lookout for computer room air conditioning (CRAC) units that squeak or rattle loudly as it could be a sign of poor maintenance. Condensation from CRAC units should be drained away immediately through piping, be on the lookout for water leaks.
Verify that there is 24/7 security enforcement. This should include offices and common areas being isolated from the data center floor, mandatory visitor/employee registration or electronic ID access and interior/exterior video surveillance. Some data centers also link visitor ID cards with a persons biometric information through the use of a palm reader. This helps to deter ID card fraud.
6. Fire Protection:
Not only should there be smoke and heat detectors, but they should be linked to an alarm panel that graphically shows the location of the fire on the buildings floor plan. The first line of defense should be a gaseous system that suffocates the fire by displacing the oxygen in the air. These systems are less damaging than water based ones but they are usually designed for fires of short duration.
Larger fires will often require a pre-action water based system. Here the pipe lines are pre-filled with pressurized air to reduce the risk of flooding during normal operation. Water only enters the piping after an alarm signal has been detected, then the sprinklers release the water only after a pre-defined temperature has been reached. False alarms are minimized by requiring two events to occur before the system is activated. This is an industry standard method of fire prevention and it should be on your checklist.
If your data center is situated on raised floor tiles, you should ask whether there are liquid detectors underneath. This helps to prevent problems due to extinguisher and CRAC unit leaks. Also in this case, make sure that the cabling lies in trays above the floor out of harms way from minor flooding.
If possible, the server area should also be isolated using fire proof doors.
7. Network Connectivity:
Not all data centers will provide you with Internet connectivity. Some will only have a demarcation point where ISPs have placed their equipment. You will then have to contract with the ISPs to extend a data circuit to your server area. Connectivity can become more complex than it first appears. There are different types of data circuits requiring varying types of adapters on your network equipment.
If you require only one link, then youll need to configure a single default gateway on your network equipment to get to the Internet. When multiple links are required, youll need to configure a dynamic routing protocol on your network equipment. This will automatically calculate which of the many links will get to the data to its final destination most quickly. It can also be used to bias traffic to and from your web site on the cheapest ISP link and will automatically fail traffic over to the remaining ISP circuits if one of the other circuits fail.
Detailed discussion of typical network connectivity issues usually requires the services of a network engineer and is beyond the scope of this chapter. Appendix II will cover many frequently used terminologies and scenarios to help you evaluate your options better.
8. Network Monitoring:
It is often taken for granted that your data center provider continuously monitors its equipment for failure. Ask about the frequency of the checks. A polling cycle of five minutes or less is generally acceptable. Also ask about the types of checks done, ICMP (Internet Control Message Protocol) or "ping" tests only check basic network connectivity and server response. The facility should also use SNMP (Simple Network Management Protocol) to track CPU, memory, error and data throughput rates. It is possible for SNMP enabled systems to send notifications, or "traps", when components fail, or a predefined event, such as high CPU usage, occurs. This information should be fed into some form of a job ticketing system that will ensure that the problem is fixed quickly. Ask about the number of failed polls that will trigger an alarm and whether they too will automatically generate a ticket.
Ensure that your data center uses multiple DNS servers, behind different firewalls, in multiple locations to prevent your web site from being affected by one of the servers going down. Some facilities will provide not just caching DNS for the exclusive use of your servers, but also authoritative DNS services to handle Internet queries for your Web domain. With authoritative services, ask about the procedures for updating DNS, the lead time for requesting changes and the format of the DNS data the provider will need to enter it into their systems.
10. Customer Support:
Ask about the availability of a web portal through which you can view statistics, billing, contact, and server information related to your site. Also ask about the times during which scheduled maintenance is done and the types of notifications that are provided. Request a summary of escalation procedures used when problems occur and whether there is a formalized means of documenting and permanently fixing problems. From time to time you may need simple services such remote hands on help in rebooting a server or changing a backup tape. Ask about the availability of such services and possibly more complex ones through an as-needed contractual or longer term retainer based agreements.
The backup system you are using at your current location may be different from the one used at the new facility. This could be the source of difficulties if you have to restore historical data during or after the relocation due to server failure or human error. Verify whether the new facility can handle data backed up using your software on your backup media. If not, you may have to invest in data conversion services with a third party.