Original URL: http://www.theregister.co.uk/2008/10/21/rackable_2u_server_rev/

Rackable stays horizontal with x64 servers

Now with more density

By Timothy Prickett Morgan

Posted in Servers, 21st October 2008 20:39 GMT

Rackable Systems might be a niche player in the server racket, but the company's server engineering has allowed it to stay in business since 1999 and still, in many ways, set the pace for density in the data center. Today, the company revved its 2U rack servers, dubbed the C2005.

Unlike the commercial blade server and chassis designs from Hewlett-Packard, IBM, Dell, and a few other tier-one server makers that have only nominal market share in blades (you know who you are, Sun Microsystems, Fujitsu-Siemens, Hitachi, and NEC), Rackable's servers mount horizontally in racks that have servers in both the back and the front of the rack.

Each Rackable machine is half as deep as a standard rack server. Rackable drives server density back-to-front instead of by packing lots of skinny servers vertically in a blade chassis and then stacking chassis on chassis. Either approach - half-depth rack or blade - requires plenty of engineering to cram the features of a standard two-socket server into what amounts to half the space or less.

The neat bit about Rackable's designs is that using half-depth rack servers in the back and front of a rack creates a kind of chimney in the middle of the rack, which lets cold air for cooling the iron to be pulled in from the data center aisles and then sucked out through the center of the rack in a manner that does not create hot and cold spots in the data center. (Yes, data centers have what can be called weather).

This is a very clever, and devilishly simple, design concept. The wonder is that more companies don't make rack servers like this. It all comes down to volume economics and the profit margins that come from sticking with full-depth rack motherboards (which is cheaper than doing engineering) or by creating custom blade boards that fit into standard racks. Every server company makes its choices and the market decides.

With the C2005 rack servers, Rackable is making the top and bottom of the 2U rack server independently configurable, with four different options on the top of the server for disk storage and two different options for the front, for eight unique possible configurations. On the top section, customers can choose to have four 3.5-inch disks, eight 2.5-inch disks, a mix of four 2.5-inch disks and two 3.5-inch disks, or two 3.5-inch disks with space on the right hand side for five low-profile PCI slots.

If customers don't need the expansion slots, they can put in a DVD drive and an internal 3.5-inch drive in the space at the bottom of the server case, and they can also put one 3.5-inch or two 2.5-inch disks behind the service processor's LCD display on the front of the server, which folds out to reveal the drives. The machines that don't have the five extra PCI slots have one PCI slot on a riser board coming off the motherboard. The C2005 supports up to ten 2.5-inch drives and up to five 3.5-inch SAS or SATA-II drives.

Like other current Rackable machines, the C2005 supports SSD drives from Intel, specifically the 32 GB and 64 GB enterprise-class drives (the X25-E in the Intel catalog) for high IOPS and write environments as well as the 80 GB and 160 GB SSD drives Intel has put out for low-write environments (these are the X25-M drives).

According to Geoffrey Noer, vice president of product management at Rackable, the typical 1U rack-mounted x64 server has two PCI slots and sometimes only one, and usually only has room for four disk drives. The move toward low profile peripheral cards - such as Ethernet NICs, RAID disk controllers, and host bus adapters - has helped Rackable's cause. These items were once exotic, but are becoming more widely available if not yet standard. To get similar feature density in the past, Noer says Rackable would have had to sell a company its C3000 3U half-depth rack server.

The C2005 is a two-socket machine that supports motherboards for both Intel Xeon and Advanced Micro Devices Opteron processors. While Rackable supports the full line of Intel and AMD chips, Noer says that the vast majority of its customers - who are very keen on low power and high density - buy Xeon LV or Opteron HE low-voltage parts. They are willing to sacrifice a little bit of performance for a lot of power and cooling reduction. Customers can use dual-core or quad-core x64 processors from either Intel or AMD, but they obviously have different motherboards.

The Foundation Series racks that are used for the half-depth servers allow 44 C2005s to be put into a single rack (that's both front and back filled), for a total of 352 x64 cores in a single rack. A normal 1U, two-socket server can have 42 servers in a rack, for a total of 336 cores, and that is only if you don't have to leave space between the machines for cooling (as you often do with rack-mounted servers). And the peripheral options on these 1U machines are limited, too. And while IBM can cram 448 processor cores into its BladeCenter H chassis, such a dense setup has minimal storage (two drives per blade) and again it assumes you don't have to space boxes out to keep from overheating.

HP's c7000 chassis can support up to 16 half-height or 8 full height blades, for a total of 512 processors maximum either way, but you have the same issues about not having much local storage and having blades packed very tightly and creating a lot of heat. Of course, this is exactly why low-voltage parts are popular among Rackable's customers. The fact is, if IBM and HP blade customers want to add a reasonable amount of storage to their blades, they have to rip out about half the blades in the boxes and buy storage modules that link to the blades. (You cannot change the laws of physics, Captain . . . .)

Like prior generations of Rackable servers, the C2005 machine offers both AC and DC power supplies. The AC power supplies are rated as high as 92.5 per cent efficiency, and the DC power supplies are rated as high as 96.5 per cent.

Rackable already sells a line of 1U, half-depth servers, the C1000s, and the above-mentioned C3000, which are 3U high. Rackable is not, by the way, against traditional rack servers. The company's four-socket Opteron and Xeon servers, the H series, are full-depth machines.

The one thing Rackable doesn't have is a list price, says Noer. Every deal is custom bid and made-to-order, which the company somehow - and quite wrongly - believes makes Rackable exempt from having to tell people what it costs to buy its gear. So even if Rackable has a density advantage, it is hard to say if it has a price/performance advantage compared to blades and in-chassis disk modules or standard rack servers. ®