This is the final article in our three-part series on the pros and cons of blade servers. Here we explore the technology...
gains of blade servers.
In part one of this series, we explored whether blades offer cost savings compared with rack servers. In part two, we examined whether data center design and power and cooling concerns tip the scales in favor of blades. Now, in part three, we examine whether advances in blade server technology make blades a viable alternative to their rack-mount counterparts.
Over the past couple of years, blade vendors have made significant technical advancements in terms of I/O, memory, network interface cards and power efficiency, according to Dave Leonard, chief technology officer at hosting company Infocrossing Inc. in Leonia, N.J.
These increased capabilities have enabled users to meet business needs with greater IT dexterity and less downtime. Bill Montgomery, chief technology officer at Lulu, an online content site, for example, cited flexibility as the reason that he has migrated away from rack servers in the company's production data center. "Blades are much easier to deploy, provision and manage," he said. With IBM BladeCenter servers and an EqualLogic Inc. storage area network, Montgomery said Lulu has the ability to accommodate fast growth quickly and with minimal system disruption.
Technology gains signal a step forward
Blades' increased reliability have paved the way for additional capabilities. "There's now a lot more connectivity into each blade with Ethernet ports, making server virtualization possible where it wasn't before, because there weren't enough ports," Leonard said. In essence, the gap between racks and blades for many processing needs has narrowed to the point where "the form factor is different, and that's pretty much it," he said.
John Enck, a research vice president at Gartner Inc. who covers server infrastructure, agreed. "The major vendors use the same chip sets in their blades and rack servers," he said.
At Lulu, Montgomery also advocated blades to enable server virtualization. Lulu runs VMware, thanks to the extended memory in its IBM blades. "We have 8 GB memory modules rather than 4," Montgomery said. While the memory modules in Lulu's blade servers have lower capacity than the latest models in rack servers, Lulu can install twice as many modules in its existing blades. "That makes a better case for virtualization on blades," Montgomery said.
That's not to say that virtualization is universally appropriate. For some data centers, virtualization on blades is a pricey proposition; because blades can't typically host as many virtual machines (VMs) as a hefty rack server, they may require more licenses to virtualize the same number of VMs as with rack mounts. "With large rack-mount servers, you pay for only one license," said Bob Sullivan, a senior consultant at the Uptime Institute Inc. in Santa Fe, N.M.
"There are certainly cost implications when it comes to licensing on blades," said Philip Skeete, president of Conxerge, a managed service provider.
A persistent gap
Thus despite blades' gains in technology and economics, there are other reasons organizations continue to prefer rack-mount servers. In fact, Gartner's Enck estimates that in 2010 rack mounts will still comprise 80% of server sales. So while vendors may push blades, rack mounts will continue to drive the bulk of business in the future.
Like it or not, even executives from the major blade server vendors concede that rack servers still have an important role to play. Both Scott Tease, worldwide product manager for IBM's BladeCenter, and Steve Gillaspy, group manager for Hewlett-Packard Co.'s BladeSystem, are quick to note that their respective companies do a healthy business in rack mounts—business that's not disappearing anytime soon.
At Infocrossing, for example, Leonard thinks that blades are on par with rack servers technology-wise, but he's still partial to rack servers. Unlike Lulu's Montgomery, Leonard says that rack servers offer him greater flexibility. "If a customer wants three servers, I can deploy them without an issue," he said. His desire to stay with rack servers may have to do with the fact that Leonard works for a hosting company whose customers are often wary of the idea of sharing a chassis with another company; otherwise, Leonard said, he doesn't see much difference from a technology perspective between rack servers and blade servers.
And then there are other factors hindering blade adoption. David Marshall, director of business development and product management at virtualization software company InovaWave Inc., notes that several characteristics of blades limit their appeal, such as shorter lifecycles, smaller hard drive space and a longer technology curve. Rack mounts typically include the latest and greatest processors before blades incorporate them.
Enck said, however, that this gap in technology is a short-term one; typically vendors release blades with comparable technology soon after rack mounts so that the rate of innovation is essentially the same.
But Enck conceded that rack mounts are superior to blades in one important area: the ability to quickly integrate changes. With rack mounts, Enck said, it's easier to swap to a PCI Express card for example, because the components within a rack server are less integrated than those within a blade. In addition, blade vendors may introduce a new chassis on a faster refresh cycle than the actual server blades themselves, and if servers aren't backward-compatible, that means an organization may have to upgrade servers if it wants the latest, greatest chassis. "There's the cost of buying a new chassis, but also it's disruptive if the chassis keeps changing," Enck said.
As a final technology concern, blades continue to present difficulties with certain kinds of workloads. According to HP's Gillaspy, blades won't suffice for very large back-end databases that require multiprocessing power on the order of 4 CPUs. On the other hand, there are certain workloads for which blades are particularly well suited. "If you have a lot of servers, like in a Web hosting operation, blades are a good choice," said Enck. "It's relatively easy to add, subtract and repair individual machines with minimal disruption."
Then there's the issue of lock-in; it's not a technology decision per se, but a factor that IT buyers care about.
"One fear of many IT organizations is the thought of vendor lock-in," said InovaWave's Marshall. "Purchasing blades, more so than rack servers, will typically lead to dependency on a single product and vendor."
Walk into most data centers, and it's not unusual to see servers from, say, HP sitting on the same rack as servers from IBM. Vendor lock-in, however, puts data center managers at an obvious disadvantage. "Customers like having two kinds of rack servers because it helps drive competition between vendors," said Gartner's Enck. That's not the case with blade servers, however. With no standard chassis size or standard blade, there's no ability to mix blade servers from different vendors within a single chassis.
That explains why more than 20% of respondents in TechTarget's 2007 Server Decisions survey cited the vendor lock-in that comes with buying a chassis as a disincentive to purchasing blades. Frames, blade interconnects and blades themselves are different from vendor to vendor and even from model to model. Mixing rack servers from different vendors and model years may not be a big deal, but it's technically impossible with blades.
On the other hand, said Enck, the potential for lock-in may explain why server vendors have invested so many resources in advancing blade server technology.
No universal right answer
But the bottom line is that neither rack servers nor blade servers present clear advantages over the other in every situation. Ultimately, the decision about whether blades are right for your data center depends on many factors -- and many that are specific to a particular company's environment.
While many data center managers remain wary of blades, others have become convinced that the platform can provide them with the processing they need without breaking the bank or compromising power and cooling requirements. Marshall conceded that blade servers got off to an inauspicious start but contended that vendors have begun to make amends, particularly in terms of technology. "Recent trends are showing significant adoption of the platform due to its increased maturity and the fact that blade vendors are listening and correcting real and perceived problems."
Let us know what you think about the story; email Megan Santosus, Features Writer.