How Cisco UCS reinvents the datacenter

If you could design a blade server system entirely from scratch, it might look a whole lot like Cisco's Unified Computing System

Encapsulating Cisco's Unified Computing System into a few paragraphs is a daunting challenge. Cisco UCS is quite unlike any other computing platform on the market today, and while there are certainly parallels to existing models, UCS carves a new path through the woods of IT. In order to relay the major differences, it's best to start in familiar territory and compare UCS with a traditional blade infrastructure.

With a "normal" blade infrastructure, you take pieces from every corner of the IT pie -- storage, network, servers, and management -- and put them together. Each blade chassis will have some number of Ethernet and SAN interfaces, either grouped using internal switching with uplinks or dedicated on a per-blade basis, and these interfaces are then connected to a larger Fibre Channel and Ethernet network. Thus, each chassis exists as an island within the datacenter, and each blade exists as an island within the chassis.

[ Peer deep inside the Cisco Unified Computing System in InfoWorld's "Test Center review: Cisco UCS wows." ]

Management frameworks surround these pieces and typically tie them together in some fashion, but the reality is that today's blade infrastructures are more akin to closely grouped banks of separate servers than a bundle or pool. That's where UCS differs significantly.

The UCS model dispenses with fixed ports and internal switching. It removes the smarts from the chassis as well. Each chassis is essentially just sheet metal and a backplane. No switching occurs within a chassis; the chassis is simply an extension of the UCS fabric, which is driven by two redundant Fabric Interconnects. These are not switches, but might be thought of as controllers.

The Cisco UCS 6120XP FI has 20 10Gb Ethernet ports and an expansion slot for 4Gbps Fibre Channel connections to a SAN. Each port can be designated as a server or uplink port, with the chassis connected to the server ports, and the larger LAN connected via the uplink ports. Drop in Fibre Channel connections to your SAN and you're done. Cabling a UCS deployment is extremely simple and requires very few cables per chassis -- up to eight if you need all that bandwidth, but four should be more than enough for most cases.

The fabric is the computer
Unlike the traditional model, there are no dedicated Fibre Channel or Ethernet links in the chassis -- everything is Ethernet. When a blade communicates with the SAN via FC, those packets are encapsulated into FCoE (Fibre Channel over Ethernet) and broken out into straight FC in the Fabric Interconnect. When a blade communicates via Ethernet, that's shipped straight out along the same pipes. In this way, Cisco has greatly simplified the overall architecture and makes better use of available bandwidth, whether for network or storage or both.

This architecture has many benefits, the most notable being immense scalability. With each chassis treated like a hot-swap line card in a switch, adding chassis is as simple as plugging them in. Since UCS chassis have no brains, they don't require any configuration. They're also cheap when compared to "smart" chassis from other vendors, since they do not have internal management or switching requirements. Thus, UCS is expensive with one or two chassis, but once you get to three, it becomes significantly cheaper.

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