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A closer look at the benefits of blades

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Blade Servers

David Berlind ZDNet.com

Published: 23 Jul 2004 13:50 BST

In response to my recent articles about blades, one that focused on RLX and another about how Dell could rock the blade market, many of ZDNet's readers wrote in to say that the comparison of 1U-sized rack-mountable servers ("What's a 'U'?") to blade alternatives was not only a legitimate one to make, but also highly relevant to the decisions they've either already made or are in the process of making.

I'm becoming increasingly bearish about blades when compared to other server form factors, such as 1Us. (That term comes from their unit of measurement. A server by that name is 1.75 inches thick.) So bearish am I, that in the traditional marketspeak of "razors and blades", I'm beginning to wonder whether the server blades aren't really the razors, and the management software to run those servers doesn't fall into the category of the blades.

Blade servers are like video or network cards that you snap into a slot in a PC. The difference is that instead of snapping them into a PC the way one would with a video card, the card (henceforth, "the blade") snaps into a slot in a special enclosure that can hold other blades. Each blade is an entire, self-contained server (usually an Intel-based one) that might include on-board storage. When storage is not on board, the blade is normally connected to networked storage such as a storage area network (SAN) or network-attached storage (NAS). Blades typically share resources with other blades. Those resources -- power supplies, networking switches, storage switches and so on -- can usually be found in the same enclosure as the blades that share them. Blades from one vendor, however, do not fit into enclosures from another.

First-tier blade vendors Hewlett-Packard and IBM and their second-tier competitors, such as RLX, Egenera and Verari (Dell won't be serious about blades until November), talk about blades as though they're the best thing since sliced bread for everyone. But are they? I'm not so sure. As far as I can tell, the greatest benefits of blades are the ones that are most difficult to quantify in terms of total cost of ownership (TCO).

For example, since much of the aforementioned resource sharing takes place through a backplane that's inside the enclosure, a blade deployment is typically void of the cable nests that might be found in server deployments involving other form factors, such as 1Us and towers. Blade vendors actually compete on the number of cables you can expect to eliminate with a fully loaded enclosure. But beyond the minimal costs that are associated with the cables themselves, cable elimination is a convenience. For some shops that have hundreds or thousands of servers that are frequently being moved (either from one enclosure to another or because of failure), this convenience may be a very important one. The same can be said for hot-swapping -- a feature that allows blades to go live on the network just on the basis of being inserted into an enclosure -- no powering up or down of anything is required.

But these are conveniences and, as it turns out, many shops that have gone with blades just plugged them in and left them much the same way they would have done with their 1Us. It's not that most server administrators wouldn't like to have these modern day server conveniences (redoing the tie wraps for the cables on my server racks was never my favourite thing to do), but the question that Dell raises, the one that was the impetus for my last column on the topic, is a fair one: should you have to pay a lot more for this convenience?