So you've decided on collocation and narrowed your list down to a few physically secure, well-configured providers. What now? Collocation services provide a premium data-center environment in which to house your equipment. The main points to consider are space, speed, feed and ping.

Housing space can be racks or caged square footage. You install your servers and connect to the provider's pipe, and you're set. Square-footage and rack-space costs can be minimized if you use ultraslim 1U and 2U servers (for an evaluation of 1U space-saving servers, see "IBM's Small Change"; for 2U servers, see "HP Takes the Middle Ground"). This equipment can be contained in locked floor-to-ceiling cages within the data center, providing an additional layer of physical security.

Adoption of SANs (storage area networks) and other storage technologies that are external to the server will speed up the adoption of small-form-factor servers. With all your storage in a SAN array, your servers need only minimal storage in a mirrored configuration to protect the boot OS. This saves on the rack space needed for the servers. The latest in stackable, rackable storage has come down in both size and price (see our online-only Sneak Preview of Network Storage Solutions' ProStor. These factors can help contain costs.

Speed and ping depend not only on the equipment you use, but also on the provider's network and its peers. The peering arrangements your provider has made are crucial. Feed is the amount of bandwidth you purchase and how much is available if needed.

Most major collocation companies have both public and private peering agreements with other network providers. Public peering is when companies connect their networks together at public IXPs (Internet Exchange Points). This allows for shared traffic, which increases bandwidth and revs up content-delivery speeds.

Private peering allows two networks to connect directly, bypassing the frequently congested public IXPs. The result is that much of your traffic will travel over private networks, not over the Internet, reducing ping time and hops. This basically means that when a packet comes onto the provider's network, it stays on a private network as long as possible before being routed onto another provider's network. This is called "cold potato routing." The opposite of this setup, "hot potato routing," is when a packet is routed off the private network as soon as possible.

Many smaller collocation companies do not have peering agreements with other providers, which means your packets won't travel first class.

In addition, companies that want to reach a global audience may want to place equipment in more than one physical facility, optimizing customer access. This is called global load-balancing. It works by determining, based on IP address, where a customer is and routing requests to the mirror site closest to him or her.

A Feeling of Security

On the broader data-security front, collocation service providers can help block DoS (denial of service) attacks and anything else hackers might throw at you. Since these attacks affect not only your bandwidth but the entire bandwidth pool for the collocation center, it's in the provider's best interests to help repel them. Internal threats must be considered as well; for example, does the facility management run background checks on new hires?

Another aspect of collocation that can help you sleep better is an SLA (service-level agreement). SLAs are contracts detailing agreed-upon measurement metrics, success/failure definitions, acceptable downtime and consequences for violation of the SLA.

When (yes, when) your service provider fails to deliver in the agreed upon manner, the SLA dictates how the provider will compensate you. Have both your network engineers and your lawyers give this document the hairy eyeball. The importance of a full understanding of your agreement cannot be overstated (for more on these agreements, see "Fishy Business.").

See Me, Feel Me, Touch Me, Heal Me

Not only do collocation arrangements eliminate capital expenditures for data-center construction -- companies also save on the incidentals, such as fire-suppression systems, security and wiring infrastructure. An IT manager can travel to the collocation center and access your equipment as needed.

The key phrase here is "as needed." One sure way to cut down on the cost effectiveness of a collocated data center is to constantly send people there to do routine maintenance. Some on-site TLC is necessary, but your planning should be done with an eye toward remote access. Servers, switches and everything else must be securely accessible from your home office. There are quite a few methods for accessing your equipment remotely, but we recommend a VPN because VPNs are generally more reliable than dial-up connections. The features of VPN clients have been expanded to include client policies for remote administration.

A convenient piece of equipment is a remote rebooter device, for performing AC rebooting of the server. One such product is American Power Conversion Corp.'s MasterSwitch Plus; a handful of companies offer similar technology. These units let you control the AC power to servers and storage devices. Many remote rebooters, in conjunction with some software and a serial connection, will let you shut down and power off a server remotely.

In addition, some companies offer remote-management boards. Compaq Computer Corp.'s Remote Insight Lights-Out Edition, Dell Computer Corp.'s Remote Assistant Card 2, Hewlett-Packard Co.'s Toptools Remote Control Card PCI and others can remotely reboot a server that has stopped responding, define as many as 12 users and provide them with access rights, perform password encryption and authentication, execute event logging, replay captured server video text, and monitor configuration information and its own external power supply.

One last thing to consider in this long list of ponderables: managed services. Collocation is following a natural progression into managed services. In this scenario, you contract for your hardware and software as well as for site space and bandwidth. Other amenities you can procure from MSPs (managed service providers) include VPN, caching, worldwide content delivery and firewall services. Most collocation providers offer managed services, and the number of MSPs is growing at a great rate. In fact, this segment of the market could eventually supplant existing collocation arrangements.

The bottom line is that you need to do what's best for your business, even if it means relinquishing some sense of control. Fond though you may be of that glass house full of blinking lights and humming servers, if it's a drain on precious resources, the time may have come to call in the contractors.