SMP Provides A Mirror Into Your Server By Scott Mason   The Intel-based symmetric multiprocessing (SMP) server market is getting a bit crowded these days. The server makers we're used to seeing--Compaq Computer Corp., Hewlett-Packard Co., IBM Corp. and the like--are building bigger and more sophisticated machines, usually in the one-to-four processor range. At the same time, manufacturers more commonly associated with large-scale, high-availability servers are making inroads into the low-end server market. NCR Corp., NetFRAME Systems and Tricord Systems are just a few of the companies building machines to compete directly with the traditional commodity server makers. These servers generally scale up to eight processors. How much server do you need? There are two things to look for in a multiprocessor server: the performance features you'd want from any server and the scalability you expect to get when you pay for extra CPUs. Once you've seen one server with four Pentium Pro 200-MHz processors, 2 GB of RAM, a dual-channel Ultra-SCSI array controller running 11 9.1-GB drives in a RAID 5 array with a hot-online spare, a dual-peer Peripheral Component Interconnect (PCI) bus, an integrated 10/100 Ethernet card, an 8X CD-ROM drive and integrated server management software, you've seen them all. That may sound facetious, but to some degree it's true. Intel representatives recently told me that server hardware is becoming a commodity, and the only way a server vendor can differentiate its product is through improved management and technical support. Many of the major server manufacturers are being forced to climb on the Intel bandwagon and are designing their machines around the Intel Standard High Volume (SHV) motherboard to avoid being late to market with a proprietary motherboard design. One example of a se rver built on the SHV board is Micron Electronics' Vetrix 2LXI. It may not have the bells and whistles of a Tricord or N etFRAME, but you can get a two-processor server with plenty of RAM for under $10,000. Manufacturers that use a proprietary board architecture can gain an advantage in performance, but you'll end up paying extra for the research and development. If you're not willing to pay a premium, you need to look at other differentiating factors--such as speeds and feeds, fault-tolerant features, server management software and "brilliant but cheap" technical support. Let's Run the Numbers If you're ready to buy an SMP server, get Pentium Pro processors. The P6 chip was designed for multiprocessing. Intel's Multi Processor Specification (MPS) defines how memory is shared among processors, and links up to four P6 processors without a separate cache bus. Maintaining cache coherency between processors inside the system this way eliminates the need for an outside cache bus. When Intel put a Le vel 2 cache into the P6 chip, it took control of that aspect of the system design away from the server manufacturers. Compaq's Pentium-based TriFlex architecture included a 1-MB L2 cache, making it faster than the first P6 servers, but Intel has since released its 200-MHz chip with 512 KB of cache. The P6 uses Error-Correcting Code (ECC) between the processor and L2 cache on a 64-bit bus. These features combine to make a system that has a data-throughput rate of more than twice that of a Pentium system with the same clock speed. There's no reason to buy a server with seven slots on the I/O bus if four of them are EISA. EISA slots, included to ensure backward compatibility with your old cards, are usually bridged off the PCI bus. The problem is once a high I/O EISA card takes control of the bus, it keeps control of the bus until it's done. EISA card performance on a PCI bus is actually slower than it would be on an EISA bus server. Since you're paying for a high-performance server, get one with plenty of PC I slots and replace those old EISA cards with PCI. To download an Adobe Acrobat .pdf format version of the SMP Buyer's Guide charts, click here.

Updated April 24, 1997