When a small to midsize business installs a new server in its data center, it has to make a number of connections, including a keyboard, a mouse, a monitor, power cables, one or more network connections, and perhaps a storage connection.

Rather than setting up all of those connections to each of a dozen servers, wouldn't it be great to have a way to consolidate them into just one of each type? A blade server system can do that very thing.

Blades are stripped-down, modular servers. Blade servers consist of a chassis (which can hold anywhere from 2 to 14 blades), the blades themselves, a management unit that allows access to each blade, and network and storage connections for each blade. Every blade is a separate server equivalent to a 1U (1 rack unit) rack-mount server, and it may have anywhere from one to four CPUs offering a range of 2 to 48 cores. Memory support can go up to 256GB of RAM.

Blades can support one or two hard drives, or the entire chassis may share a storage system with six or more drives. In addition, the chassis requires only one keyboard, mouse, and video connection (or a separate management connection); two power connections for redundant power supplies; and one network connection. Many blade chassis also offer Fibre Channel or InfiniBand connections to each blade.

Why you should install blades

Some people may assume that blade servers are used only in large enterprises, and are not suitable for small businesses. This is not necessarily the case; any organisation that uses more than three or four servers may find blade servers a good fit.

Blade servers offer a substantially simplified cabling setup versus the equivalent number of separate rack-mount servers. They make management easier, too, since one interface - rather than seven or more separate interfaces - can manage all the blades. In addition, they often can squeeze more equipment into a given amount of space than separate setups can: A space that's 7 rack units (12.25 inches) high, for instance, may hold from 8 to 14 blades.

Since the blade system can also incorporate storage and network switches, plus fault-tolerant storage, you may save even more space. This can be both good and bad - although the system uses less space, it can produce more heat, possibly requiring more or specialised cooling.

Pricing for a chassis is about the same as the cost of an equivalent number of separate servers. In fact, the blade system might be more expensive, but the lower management costs of the blades over its lifetime will probably more than make up the difference, as long as the system is fully utilised.

You can buy some systems with less than a full complement of blades and purchase more blades as you need them; if this appeals to you, however, check how long the existing blades have been in production, and whether earlier blades can work in the same chassis. You don't want to buy a system and have the blades be out of production by the time you need more.

One big trend is to use virtualisation to consolidate many operating systems into a single large hardware setup. If this is something you're considering, a blade system may not be the best choice for you. Although it is possible to use blade servers and virtualisation in conjunction, systems that run several to dozens of OSs on each of many blades are probably beyond the needs of most small businesses.

If you're keeping a number of separate hardware servers - either because you don't want to deploy virtualisation or because you're running applications that fully use the hardware they're running on - then blade servers can reduce the cost of managing the systems.


Blade servers have some limitations compared with separate servers, though. The first is expandability: While even 1U servers may have two or three PCI-X or PCI-E slots, blades may not have any. Separate servers also typically support at least four drives, providing more storage capacity and performance than you can get from the one or two 2.5-inch drives typical for blades. (Some blade systems, though, offer high-performance Fiber Channel connections or 10 Gigabit Ethernet connections to each blade, or shared high-performance storage.) If you need specialized hardware, blade systems may not be an option.

Whether blade systems are a fit for a business has less to do with the kind or size of the business itself than with the organisation's IT demands. If your business tends to buy one or two servers a year, justifying a blade system is difficult. If you typically purchase clusters of 4 to 12 servers, the savings in management costs and potential power consumption may make buying blades worthwhile. Since the blade system could cost more initially, an organization with a single administrator might not save enough in management costs to make up the difference.

Differences Among Blade Servers

On the market you can find a number of enterprise-oriented blade systems from vendors such as Cisco, Dell, HP, IBM, and Sun, as well as from smaller vendors such as Acma, PogoLinux, and SuperMicro. Such systems typically use differing hardware, so blades from one system cannot be used in another chassis, or even in older (or newer) versions of the same vendor's chassis. The systems also differ substantially in how they are managed, what connections they offer, and, of course, in the number of blades and processors, the maximum memory and drives per blade, and cost.

It's not necessary to spend $50,000 or more for a blade system. You can choose small, 1U, two-node systems that start at under $2000, and chassis that hold four blades with starting prices under $5000. Ordering these systems is much the same as ordering individual servers, except that you need to look closely at network and storage options to ensure that each blade has the capacity you require. Processors and memory are available in the same varieties and capacities as they are for standard servers - some blade systems even offer both Intel and AMD processors in the same chassis, as well as blades with up to four 12-core processors.

Benefits and Drawbacks

Blade servers can reduce management costs, save power, free up administrators for other tasks, simplify data-center cabling, and enable remote administration without extra equipment (such as KVM over IP switches). They also offer better reliability than individual servers, with options such as dual redundant power supplies and high-availability components.

The biggest problems blade systems may introduce are power and cooling requirements. Since blade systems can fit more CPUs, memory, and other components into smaller spaces than other systems can, they might produce more heat, and may need more power. Some blade systems can pack 672 CPUs into a standard 7-foot rack, which would require 38,400 watts of power and would produce more heat than a commercial-grade oven.

Since many blade systems are available for purchase with less than a full complement of blades, you might buy a system with a few blades and get more as required. But with hardware standards evolving so quickly, even after a period as short as 18 months the blades you purchased with the system might no longer be available. Finding out whether previous versions of blades are still supported will give you a good indication of whether new blades with faster processors and memory are likely to be compatible with the half-full chassis you already have.