algorithms
There are 10 entries for the tag algorithms
The choice of load balancing algorithms can directly impact – for good or ill – the performance, behavior and capacity of applications. Beware making incompatible choices in architecture and algorithms. One of the most persistent issues encountered when deploying applications in scalable architectures involves sessions and the need for persistence-based (a.k.a. sticky) load balancing services to maintain state for the duration of an end-user’s session. It is common enough that even the rudimentary load balancing services offered by cloud computing providers such as Amazon include the option to enable persistence-based load balancing. While...
Knowing the algorithms is only half the battle, you’ve got to understand a whole lot more to design a scalable architecture.
Citrix’s Craig Ellrod has a series of blog posts on the basic (industry standard) load balancing algorithms. These are great little posts for understanding the basics of load balancing algorithms like round robin, least connections, and least (fastest) response time. Craig’s posts are accurate in their description of the theoretical (designed) behavior of the algorithms. The thing that’s missing from these posts (and maybe Craig will get to this eventually) is context. Not the context...
It comes down to this: the on-demand provisioning and elastic scalability systems that make up “cloud” are addressing NP-Complete problems for which there is no known exact solutions.
At the heart of what cloud computing provides – in addition to compute-on-demand – is the concept of elastic scalability. It is through the ability to rapidly provision resources and applications that we can achieve elastic scalability and, one assumes, through that high availability of systems. Obviously, given my relationship to F5 I am strongly interested in availability. It is, after all, at the heart of what an application delivery...
That doesn’t mean it isn’t hard - it means it’s a different kind of hard. For many folks in IT it is likely you might find in their home a wall on which you can find hanging a diploma. It might be a BA, it might be a BS, and you might even find one (or two) “Master of Science” as well. Now interestingly enough, none of the diplomas indicate anything other than the level of education (Bachelor or Master) and the type (Arts or...
Infrastructure 2.0 enabled application delivery platforms have more than a few things in common with the Transformers. Like Autobots, there’s more to it than meets the eye. If you’re familiar with the mythology of the Transformers – and perhaps even if you aren’t – you know that they key attribute of Transformers is their ability to take on “alternate modes” such as cars, trucks, and winged vehicles simply by scanning the object and then adapting their own form to match. One of the key premises of Infrastructure 2.0 is also the ability of network and...
The wrong load balancing algorithm can be detrimental to the performance and scalability of your web applications. When you’re mixing and matching virtual or physical servers you need to take care with how you configure your Load balancer – and that includes cloud-based load balancing services. Load balancers do not at this time, unsurprisingly, magically choose the right algorithm for distributing requests for a given environment. One of the nice things about a load balancing solution that comes replete with application-specific templates is that all the work required to determine the optimal configuration for the load balancer and...
A load balancing algorithm can make or break your application’s performance and availability It is a (wrong) belief that “users” of cloud computing and before that “users” of corporate data center infrastructure didn’t need to understand any of that infrastructure. Caution: proceed with infrastructure ignorance at the (very real) risk of your application’s performance and availability. Think I’m kidding? Stefan’s SOA & Enterprise Architecture Blog has a detailed and very explanatory post on Load Balancing Strategies for SOA Infrastructures that may change your mind. This post grew, apparently, out of some (perceived) bad behavior on...
How to optimize compute resources in a heterogeneous environment using weight/ratio-based load balancing Unless you’re starting from scratch your data center is full of physical servers of various and sundry sizes, colors, shapes, and compute resources. And even if you’re starting from scratch and you have beautiful racks of everything the same, it’s not likely to stay that way if for no other reason than, well, hardware moves on at an astonishing rate these days. So you’ve almost certainly got (or will have) a physically heterogeneous environment in terms of hardware compute resources. When you’re scaling...
Greedy algorithms can result in the right solution in the end, but rarely do Don and I were having a discussion with our oldest son the other night about writing a chess program. There are myriad options for implementing the learning aspects of a chess program, but this is not a task for the timid. He ended up proposing a much simpler solution (this was just an exercise in ‘can I write it’, after all) that would have essentially used a very greedy algorithm; one that made a decision regarding the computer’s next move based on current state of...
ArsTechnica has an interesting little article on what Windows Azure is and is not. During the course of discussion with Steven Martin, Microsoft's senior director of Developer Platform Product Management, a fascinating – or disturbing in my opinion – statement was made: There is a distinction between the hosting world and the cloud world that Martin wanted to underline. Whereas hosting means simply the purchase of space under certain conditions (as opposed to buying the actual hardware), the cloud completely hides all issues of clustering and/or load balancing, and it offers an entirely virtualized...
