Additionally they use a critical enclosure bay, removing one of the potential slots necessary for a blade enclosure to provide server density. So an eight bay blade enclosure with two small storage blades would only be able to house six blade servers.
Obviously buying a blade enclosure does not mean that you have given up the ability to also use rackmount servers when appropriate. You can continue to mix and match. But to obtain the numbers necessary for a small business to cost justify the blade infrastructure often requires that purchases lean heavily toward blade servers to fill the enclosure(s) as densely as possible.
Much of the danger of blades is in the potential for lost opportunities. Small businesses especially function best and compete most strongly against larger businesses by being flexible and agile. Blades are the opposite of agile. They require large, upfront infrastructure planning that includes technological, physical and geographic lock-in.
Even if a business plans ahead and sees no obstacles to adoption this does not mean that opportunities will not be missed in the future. This could be caused by a lack of flexibility to adapt to changing business conditions effectively.
Once a blade enclosure is in place, purchasing decisions almost certainly are made based on the investment already made and no longer on simply what is best for the company. This doesn't have to happen but almost certainly will. Naturally, the existing investment needs to be protected.
All of this being said, blade servers can still make a lot of sense for certain businesses. Blade servers generally consume less power than their non-blade counterparts due to their shared system components. Be sure to consider the power consumption differences in the storage area, however, as blades push power consumption from the server to the SAN and can often be misleading as to where the power is going. A savings in one place is only valuable if the cost does not appear again in another.
Blades are easy to transport and relocate when enclosures are available. This can be a bigger factor than is obvious, especially when it means that there are several additional staff members capable of relocating a server. Almost anyone can lift and move a blade server.
When combined with a very aggressive SAN infrastructure, blades can be very beneficial to a virtualization environment. This combination gives the maximum cost and flexibility advantage to businesses large enough to leverage it.
The SMB market mostly consists of businesses for whom this would be very prohibitive, though, and this solution will continue to be relegated to businesses at the larger end of the SMB spectrum.
Virtualization will, in fact, reduce the number of servers needed by most businesses, making it even harder to justify blades to smaller businesses. Where previously a dozen or more servers would have been needed, today only two to four are needed to not only meet but to surpass earlier service levels.
If you can support adequate densities or get really aggressive vendor incentives then blades can be quite cost effective, if you calculate against your risks. Blades are always a little more risky, but if your cost is reduced significantly in buying them then they may be very much worth the risk in flexibility.
The cost of the enclosure is a key factor here. If your enclosure is free then suddenly the cost savings of a blade system can be enormous - especially if a large number of blades are purchased, providing really good enclosure density.
Blade servers are a great technology and show a lot of promise for the future. As enclosure lifecycles slow, new technologies emerge, costs are reduced, volumes increase and, hopefully, as vendor-neutral standards emerge Im confident that blades will become the de facto standard in even the smallest datacenters.
I see this as taking at least another market cycle before this will really occur. Most likely, in my opinion, it will be another five to seven years before the form factor truly displaces the rackmount server in general utility.
Scott Alan Miller is an IT Manager, Strategist and Engineer who has been working in IT for over fifteen years primarily in the financial, healthcare and SMB markets.