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Blade or brick, take your pick: both increase server power, not server numbers.

Many organizations want to increase their server power without increasing or replacing their servers, especially at busy network edges serving firewalls and domain names. The industry has responded by developing server blades and bricks, which are modular servers with smaller form factors for dense processing power. Bricks are computing blocks made up of memory, processors, or storage operating systems. These blocks can be assembled inside chassis to form larger and more-complex computers. (Dell remarked that its bricks' similarity to Lego designs is no accident.) Blades consist of cards with server functionality, which are inserted in a rack to share power supplies and network connectivity. Manufactured by companies like RLX Technologies, server blades exist in edge, department, and workgroup deployments where they offer cheap, high-density processing at moderate performance speeds. These high-density server environments have implications for data storage, especially with high-density, high-performance blade s and bricks scheduled to ship in 2002 and 2003.

Steve Berens, director of marketing at Benchmark, said that r blade environments definitely impact the way storage is handled: "A very dense server configuration requires a very concentrated storage configuration." Storage products that support blade deployments include both disk- and tape-based backup, including Dot Hill's RAID Blade and Benchmark's ValuSmart Tape 640 Blade. These are storage units with small form factors that can receive incoming data in parallel, a necessary quality in a dense server environment. Berens sees economic factors as important in blade storage configurations. He said, "For the next couple of years at least, budgets will not be as free flowing as they were. In this environment, people are looking to take maximum advantage of the dollars they have today. As long as we can deliver a scaling incentive to storage, that's where they see the big advantage. If you make these devices like a network printer where it's simple to attach it to the network interface and it works, that's the model we're using."

Dot Hill's Omar Barraza, director of product management, said that blade servers do present specialized storage issues because of their high density. Dot Hill released its RAID Blade a year ago to serve 1U and 2U server environments. Barraza said, "Dot Hill is taking blade servers under consideration. That's one of the reasons we developed Axis storage manager. However, I think customers are going to wait until the performance of blade servers approximates the performance of traditional servers." Anticipating that Axis would need to manage blade servers, Dot Hill kept it to a 1U form factor.

Blade Servers in the Data Center

Several major vendors--including IBM, Sun, and Dell--have recently announced that they're developing blade or brick servers for highend data centers. These servers maintain high density and are highly configurable, but also offer high performance, availability, and manageability. Storage will become even more. important in these high-end-blade-server environments as blades infiltrate data-intensive glass houses.

Though all of these blade manufacturers mention storage components, Dot Hill's Barraza wonders how well blades will scale to high performance environments, and how that will impact storage. There is no internal storage for existing blade products--the compact cards contain no disk, and, although bricks would include modular disk storage, they are not out of the R&D stage. But as performance grows, blades will scale up from network servers to application servers. This will require some sort of storage networking.

Blades can reach up to 300 cards in a standard rack, leading to very dense data movement requiring scalable and flexible storage. Customers that have deployed this type of server configuration will likely want the same flexibility in their RAID arrays and tape autoloaders, where they can economically and simply increase storage capacity in a rack-mounted configuration. For example, backing up to multiple tape drives enables more efficient parallel backups, while installing multiple devices like lower-cost RAID drives grants redundancy.

IBM plans to introduce high-performance server blades for data center, clustering, and grid environments. BladeCenter will focus on running full-fledged applications on a blade platform, using its Director Tool to manage the multiple processors. It will integrate servers, storage, and networking. Jeff Benck, director of xSeries eServer said, "Many people talk about blades being a smaller server factor. We have a different vision."

Benck believes that many customers adopting blades want to accomplish server consolidation by harnessing centralized blade management, but they don't want to give up performance for density. IBM plans to leverage its own storage division with a comprehensive set of integrated blade storage products that will support local storage in blade environments.

IBM is planning to roll out its blade servers with internal IDDE storage, and will support SCSI HotSwap drives as an option. Near the end of 2002, IBM plans to introduce a two-bay form factor NAS appliance for blade servers.

Dell is also planning on a blade launch in the second half of the year. It will introduce a blade server first, and in 2003 a brick server product. Its brick chassis will contain customized combinations of server, storage, and network connections. Darrel Ward, a senior architect with Dell Enterprise Systems Group, said, "Bricks and blades treat storage different in the amount of flexibility and options the customer has. That type of flexibility is critical to high-end data center customers, because you add a lot of diverse needs. You must be able to maintain density without asking the customer to give up flexibility and options."

Internal storage modules will sit right in the chassis, and will contain standard disk drives. Externally, the chassis will have optional network interconnects for SCSI, Fibre Channel, and InfiniBand, with iSCSI following shortly.

Network Interconnects

To handle rack storage for blade servers, IBM plans on adding rack-mounted NAS devices and network interconnects on the server rack backplanes. One of the questions surrounding external storage is what network connect will likely handle most blade server environments. The name of the blade game is density plus high performance, but in high-performance environments dense data causes backlogged storage. InfiniBand architecture may help as it adds more switches to enable more network paths, relieving latency by offering a high degree of interconnection over the same amount of bandwidth.

However, Benchmark's Berens is counting on iSCSI instead, since InfiniB and is optimized for disk-based storage and not tape. iSCSI, built on the common iSCSI standard, is more amenable to different types of storage devices such as tape. Dot Hill's Barraza added, "Fibre Channel SANs are mostly being used for database servers, while most application servers are NAS and DAS, and will be iSCSI. We believe that the majority of storage for the blade servers will probably stay on IP."

However, according to Dr. Ramon Acosta, vice president of industry initiatives at Lane 15 Software, SRP (SCSI RDMA protocol) does allow InfiniBand users to send SCSI commands over InfiniBand fabric. If the fabric is bridged to a Fibre Channel SAN, the SCSI commands are transparently converted to Fibre Channel commands in the router. Although not an official industry protocol, SRP can act as a standard protocol by talking directly to InfiniBand DAS devices, or by entering a router for Fibre, Channel storage. SRP passes SCSI commands, which are independent of the network or fabric the command is traversing. Once the SRP protocol encounters the storage device, the device sees only SCSI commands. Acosta finds it likely that InfiniBand blades or blades with InfiniBand and connects would natively support SRP.

Most developers plan on connecting high-performance blade installations to a SAN. Barraza added, "As the blade servers get faster, they'll outpace the ability to go highspeed NAS. They're going to move to the SAN or maybe DAFS, or some other block-oriented approach. They don't have to share files, why pay the performance penalty for that?" According to Harold Pike, IBM's business development executive in IBM Storage Systems Group, blade storage presents much more opportunity than NAS' appliances. Eventually the blades might also connect to a Fibre Channel SAN via a fiber interconnect on the backplane. IBM's 2003 plans include integrating BladeCenter with its StorageTank storage strategies.

Will there be blade server SANs? Barraza envisions a blade server doing block processing, but believes that blade server SANs will be IP-based running over iSCSI. This is because blades are already economical Ethernet servers, and changing the network configuration, as opposed to adding back-end interconnects, is cost prohibitive. Barraza said, "I think blade servers will do more than anything in separating SAN and Fibre Channel. Customers will realize that SAN is really the process of doing block storage over the network." Benck pointed to BladeServer's high performance and integration capabilities, which might allow them to serve as a SAN front-end. "What new solutions can be developed as you integrate storage networking and servers together in a platform?"

Good question and worth finding the answers to. We'll probably get the chance: IDC has issued a conservative forecast of one million server blade units shipped by 2004, an 80% increase from 2002.
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Author:Chudnow, Christine Taylor
Publication:Computer Technology Review
Geographic Code:1USA
Date:Jul 1, 2002
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