Server blades: Density versus flexibility
A real advantage to dense blade deployment is the ease and speed with which you can add more servers. Rather than wasting hours installing yet another incompatible rack-mounting rail kit, administrators can plug in a new server in mere seconds. Replacing a damaged server is just as easy. Each blade is completely independent of the others--inserting or removing a blade has no effect on any other operational blade in the same chassis.
While companies such as Dell and Compaq have announced plans to release server blade products, two vendors are already shipping products. The first to market was startup RLX Technologies, with its RLX System 324 product. HP is the first major vendor to market with its blade server. The two companies' very different approaches to blade servers suggest that the emerging blade server market may take some time to converge on standards useful to a majority of customers.
The RLX blade
RLX has chosen to create a product with an emphasis on reduced physical density and power consumption. Although startup RLX has faced tough times trying to break into the server market, it has attained some level of legitimacy through a sales agreement with IBM, which is actively selling RLX's product line to enterprise and data center markets.
A traditional 7-foot-tall rack--which holds around 40 1RU (1.75-in.) servers--can hold up to 336 server blades from RLX. This incredible density is due to the incorporation of Transmeta's diminutive Crusoe processor. The use of Crusoe also translates to power savings; each Crusoe-based blade consumes an average of only 7 watts of power while running. (A maximum of 15 watts is supplied to each RLX blade, compared to 75 to 120 watts for a traditional server.) RLX's approach could reap considerable savings, not just in terms of power bills, but also by reducing the need to purchase costly hardware such as UPS, generator systems, and cooling equipment.
Why Crusoe?
The Crusoe processor in the RLX System 324 combines hardware and software to offer the best possible balance between performance and power consumption. Most processors offer the ability to slow down when they get too hot, but there are usually only two choices available: slow and cool versus hot and fast. Transmeta's LongRun technology lets the processor continuously adjust speed to offer the best compromise between performance and power without overheating the processor.
But Crusoe is a not a computational powerhouse. It works very well for most everyday Internet server uses (Web, e-mail, and file serving) since most networked servers are not CPU-bound. But it would not be a good choice for a high-end database, application server, or anything else that requires significant processor muscle.
Crusoe is also a somewhat risky choice for RLX. Transmeta is having a difficult time gaining significant market share against Intel, and the market downturn has not improved the situation. Many companies may be cautious about choosing RLX for fear that Transmeta may die off, leaving them with an orphaned technology. But RLX designed its management software around open standards (SNMP) and open source software written mostly in PHP. In the short run, it's unlikely that either company will be shutting down its shop.
Todd Underwood is chief technology officer at Oso Grande Technologies and a contributor to ZDNet Tech Update.
An RLX System 324 blade includes a 633MHz or 800MHz (expected in Q1 2002) Crusoe CPU, 128 to 1GB of RAM, and up to two hard disks (either 10GB or 30GB each). Each blade comes preinstalled with Red Hat Linux 7.2, a fully-licensed version of Windows 2000 Professional, or Windows 2000 for Web Servers. (Windows 2000 for Web Servers is a special license-restricted copy of Windows 2000 that cannot run groupware such as Exchange or Domino, but is ideal for Web serving at a significant cost-savings over the full Windows 2000 server OS.) RLX will also ship a bare blade on which you can install any Intel-compatible operating system. (FreeBSD, NetBSD, and OpenBSD are also known to work, but are not supported by RLX.) The blades plug into a chassis which supplies power, network connections and other management infrastructure. Every chassis component is redundant except for the midplane (into which the blades are plugged), which has no active components. Two chassis models are available: a 3RU (5.25-in.) unit that holds 24 blades and a 1RU (1.75-in.) unit that holds six blades.
Each RLX blade sports three 100Mb Ethernet network interfaces, referred to by RLX as public, private, and management. The network interfaces for all blades are aggregated to four RJ-21 plugs (big, Centronics-style connectors) on the back of the chassis, and a single RJ-45 for management. Along with two power connectors, a total of only seven cables are needed to provide power and three network connections to each of the 24 blades in a 3RU rack (compared to as many as 168 cables for 24 traditional servers, plus keyboard, video, mouse, power, and three network connections). This meager amount of cabling is a huge advantage for dense installations, as it avoids the normal mess of cables that accompanies the installation of dozens (or hundreds) of servers.
HP's blades
HP's approach to blade servers differs from RLX's, focusing on open standards, multiple vendors, and flexibility rather than on power and density. The HP blade server product is built entirely around the CompactPCI specification. CompactPCI is a bus specification that takes the existing PCI standard and improves hot-swapping capabilities for industrial and telecomm applications.
HP took this standard--which has long been in use in the telecomm industry--and used it to build a product that they hope will be a new platform for multi-vendor development. HP is already seeing some success, with five vendors having already released products that incorporate the HP blade server platform. HP's Brian Cox says that "dozens of companies are already announcing products under the Partner Program, including firewalls, load balancers, caching, and Web serving products." It is interesting to note that by focusing on CompactPCI, HP was able to develop its blade solution rapidly. Meanwhile, HP competitor (and possible merger partner) Compaq, which plans to release its ProLiant BL blade server line in early 2002, has rejected CompactPCI as being too slow to serve their product's needs. This has delayed Compaq's blade product while they develop their own data and power bus.
HP's blade server chassis (or platform) includes slots for 16 blade servers, 16 storage servers and 6 management or network blades. The 13RU chassis doesn't significantly improve on the server density that standard 1RU servers provide (13 servers in the same amount of space), but it lets administrators include storage and networking services with simple servers in the same unit; this arrangement increases the effective density for installations with significant storage and networking requirements. Moreover, because HP's blades are larger in size and require more power than the RLX blades (50 watts compared to 15 watts), HP's blade environment allows for a larger variety of blades that can perform functions such as Web or database serving, network filtering, and media streaming. As such, HP is more directly targeting the enterprise market where flexibility is valued more than density or power consumption.
HP's blade is built around a 700MHz Intel Pentium III, with 512MB RAM and a 30GB hard disk running Linux (Red Hat, SuSE, and Debian are shipped with each system). Cox says that he expects HP to ship blades that support Windows 2000 early next year; further plans include blades that employ the PA-RISC architecture for HP-UX, HP's Unix operating system, and more specialized blades from other manufacturers. This last point is key to understanding HP's strategy: Cox states that HP wants to build a new, "open market" of blades for their platform, and that by helping other manufacturers build and sell blades, they can significantly decrease costs and increase the size of the market. HP also plans to release server blades with multiple processors, processors from Transmeta, as well as blades designed exclusively for SCSI and Fibre Channel storage. It is clearly HP's hope that bringing an open standard to the table and delivering more power and space to each blade will attract other manufacturers to their product.
Other blade vendors
Dell and Compaq have both announced their intention to release products, but neither company was willing to discuss details. Bruce Anderson, spokesperson for Dell, says that Dell believes the server blade market is important, but still maturing, and that as the market stabilizes and increases in volume, Dell will release a product to address the needs of enterprise customers, likely at the end of the Q2.
Flexibility versus density
To attain the amazing density and low power requirements, the RLX blades use a proprietary data and power bus designed almost exclusively to reduce power and heat but, as a by-product, they suffer from a lack of flexibility. The RLX product will likely never support multi-processor blades without a significant redesign--there's just not enough power--and as a result, the company likely will not be able to attract other vendors to market blades to its platform.
HP's more flexible solution offers a variety of implementations, including servers, networking, and storage products, all of which can live in the same chassis. As a result, though, their blade solution requires a lot more power and offers significantly less server density than the RLX blades--only 48 servers plus 48 storage blades can be housed in an HP rack compared to 336 for RLX.
RLX's blade servers should appeal to Web hosting companies and corporate data centers--primarily those focused on providing Internet services. The HP blade server environment is more likely to appeal to corporate customers looking for a way to consolidate networking, storage and server products in a single, easier-to-manage chassis. Regardless of the specific direction the blade market eventually takes, the advantages of the server blade architecture for enterprises are too great to ignore.