Blade servers vs. rack servers
Which server form factor is better for your datacentre?
By Tom Henderson, Rand Dvorak, Network World | Network World US | Published: 01:00, 04 February 2008
The cost of the IBM blade server configured with the maximum 14 blades is US$117,400. Add power consumption (except for the cost of cooling), and the total becomes $123,900. The equivalent number of x3550 1U servers at $7,900 comes to $116,700. When the cost of the needed six-port 10G Ethernet and 24-port Gigabit Ethernet switches and power consumption costs are added, the cost climbs to $129,200. The x3650 has a total capital cost of $129,800 ($9,300 each), and with the aforementioned 10G Ethernet and Gigabit Ethernet switches plus power consumption, the cost comes to a whopping $150,700.
In the widest stretch, between the loaded BC-H vs. an equivalent number of x3650 servers, there is an 18 percent price differential over five years. This becomes amplified if power costs increase over our - admittedly very inexpensive - three cents per kilowatt-hour, which is a typical price for a large NOC in the Midwest, where we tested this gear. In the UK, powerIn other parts of the country, power can be more expensive and subject to peak use rates.
Servicing blades ultimately is faster than servicing rack servers for several reasons. First, the overall size and weight of a blade is easier to handle, because its power supply is common to other components. We could pull a blade from a server in about three seconds, whereas pulling a rack server took more than a minute, even when cable-management components were well designed and implemented. It would take much longer if a rack were in any state of disarray.
We measured how long, once a unit was out of a rack, it took to change memory or a hard drive - the two components most frequently changed by a server administrator. In this case, the times were much the same. The time needed to reinsert equipment and bring a server back online was far faster with a blade server than with a rack server, because no cables needed to be reconnected.
There is much to be said for how using blades reduces the number of power cables needed, as power cables are reduced from as many as 80 to eight. The number of copper or fibre Ethernet cables also is reduced dramatically, as well as the clutter that cables introduce and the air-flow reduction that they represent.
Additional costs are associated with management components. In the case of the IBM servers we tested, we used IBM Director to manage both types. Director must be "housed" on its own rackable server or blade, and the server has its own set of costs, though it need not be a high performer with lots of storage.
We downloaded various operating systems, including several instances running via EMC's VMware ESX, and configured them on the blade and rackable servers using Director. Some vendors charge per installation or per server for management components, and it's important to check how much these valuable and time-saving applications will cost.