Alternative approaches to maximising performance without adding bandwidth

Beating bottlenecks with network attached processing and interface cards

Users and suppliers alike are waking up to the idea that there is more to networking than adding fatter and fatter pipes. And this is happening on both sides of the Atlantic, for once.

I have previously written about the work that the likes of Zeus in the UK and F5 Networks in the US have been doing on the Layer 4-7 stage, taking server load balancing and network traffic management into new dimensions.

Two further, and different, approaches to application optimisation are network attached processing (Nap) from Californian start-up Azul Systems, and the Etherfabric server card, developed in Cambridge by Level 5 Networks.

Azul Systems has taken the idea of network attached storage and turned it on its head, so that a cluster of processors is made available on the network for whichever application needs processing power at a particular time. The aim is to improve application performance and reduce the number of servers required, thereby eliminating costly and difficult tasks such as capacity planning and over-provisioning.

At the same time, side benefits accrue, not least a dramatic reduction in power requirements and datacentre space, according to Azul's chief technology officer Scott Sellers. This is not something that should be taken lightly.

According to an IDC survey, the US server installed base alone will grow by nearly 50% between now and 2009 to more than 14 million servers installed. IDC estimates that the raw electricity consumption to run these servers will be in excess of £2.8bn per year by 2009.

How, then, does the Azul Nap work? Basically, it sits at the application server level, in front of the server pool, forming what Azul calls a "compute pool". This processing resource is made available to all applications and can be prioritised in many different ways to assign processing power to individual applications as and when they need it. So there is no 1:1 relationship between server processor and storage, added to which, Nap is operating system agnostic.

The current limitation is that the Azul technology - sold as a range of rack-mount appliances with between 96 and 384 processors in each appliance - is purely designed to support Java-based applications, though support for Microsoft's .net is coming. The good news is that there are plenty of Java-based applications.

Offloading the processing requirement from any device at any point on the network has to be a good thing. At the applications server, this problem becomes critical - a point identified by Level 5 Networks and which is fundamental in its approach to technology development with its Etherfabric network interface card. Here bandwidth provides us with few solutions.

TCP/IP may be the de facto networking protocol, but that does not mean it is actually any good. In truth, it is alarmingly inefficient in its basic form, generating enormous amounts of requests and connections for any single application and single user. Times this by thousands of users and several applications and the result is a frighteningly high number of TCP connections at any one point in time.

All the basic elements of a network server are potential bottlenecks. At low utilisation levels, all the component parts - unstressed - are able to cope with delivering satisfactory performance to the user base. The same applies to high-performance computers. But when the heat is on, as CPU utilisation goes through the roof, that is when the relationships between these key elements on a server become strained to breaking point.

As a result, performance suffers heavily, sometimes to the point of application unavailability or, at the very least, unacceptable levels of data delivery.

Here, again, network bandwidth is largely irrelevant. So, with its Etherfabric technology, Level 5 has effectively reinvented the server network interface card, with a view to optimising server components such as CPU and memory.

The company claims that, unlike alternative I/O acceleration techniques (such as Infiniband or TCP Offload) Etherfabric remains completely compatible with the existing Ethernet/IP network and application programming interfaces, so users are not required to compromise standards-based compatibility for higher performance. In other words, you do not need to change your network and applications in order to accommodate this new technology.

So how does it do this? One of the primary features of the Etherfabric technology is that it creates a separate, virtual IP stack for each application, so providing more CPU cycles per application. It enables applications to effectively bypass the operating system and its kernel - seen by Level 5 as a major bottleneck in network performance.

According to the company, the Etherfabric hardware is designed to allow multiple applications to access it directly and simultaneously, and does not depend on the operating system kernel to mediate between accesses, thereby avoiding that problem area. This architecture establishes a direct data path between each application and the network hardware, bypassing the kernel entirely, so each application sees its own interface to the hardware.

The problem of scalability is also seemingly dealt with as the Etherfabric architecture has been designed to support 10gbps and beyond. Though bandwidth is not the key element to improving application performance on a network, the need to support the forthcoming generations of Ethernet is obviously a primary requirement for any technology development.

The same applies to compliance with existing Ethernet standards. Forcing users to throw out what they already have in place has never been a smart or successful play for a supplier, especially in the long term. Level 5 Networks therefore believes that its 100% adherence to Ethernet standards is a key differentiator of Etherfabric, when comparing it with competing technologies.

"Etherfabric remains completely compatible with the existing Ethernet/IP network and application programming interfaces, so users are not required to compromise standards-based compatibility for higher performance," said Craig Easley, director of product marketing at Level 5.

What we have here then, is the reinvention of Ethernet without bending any of the existing rules. Interesting.

About Steve Broadhead

Steve Broadhead runs Broadband-Testing Labs, a spin-off from independent test organisation the NSS Group.

Author of DSL and Metro Ethernet reports, Broadhead is involved in several projects in the broadband, mobile, network management and wireless Lan areas, from product testing to service design and implementation.

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