Saturday July 16, 2022
Introduction
A long time ago in a land far way…. Someone dreamed up the concept that all Application Delivery Controllers (ADC’s) would be measured on throughput. To be fair, you need something to measure how one appliance gets compared to another. Otherwise, how do you know how powerful a certain appliance really is at processing traffic compared to something else?
As a measure it is imperfect, but it works. I say it is imperfect, as some workloads have different characteristics and as such might present a different type of load for an ADC. As an ADC vendor, Citrix can handle this in a few ways.
We build appliances that can scale across a wide range of throughputs, the idea being that you might want to start small and scale up as your service demands it. This is achieved without having to swap the appliance out as often as some other appliances. As an example, we have a single appliance that can scale from 20 GBps up to 120 GBps of throughput. We also look to have market leading SSL performance, as generally the heavy lifting is in the processing of SSL/TLS traffic.
That sounds cool, however if that capacity is tied to a box in my Dallas DC, it isn’t going to do much good when London blows up because there is a run on the stock market. What about if the workload starts off as a virtual instance and now needs to be hosted on a physical system? Needing to buy more capacity half way through a project isn’t ideal......
What is needed is something that offers the business some flexibility when unexpected events occur, this will allow IT to respond quickly and even anticipate demand changes by better monitoring.
Hold the front page!
We can solve for this. A few years ago, we uncoupled the capacity from the physical appliances and moved to a subscription ‘pool’. This pool allows for those cases where your business demands that capacity is moved where it is needed. Once an appliance is converted you can even dynamically re-allocate capacity as you need to, this brings in the option of follow the sun capacity assignment. We also made it portable such that you can transition between virtual and physical form factors.
How does it work?
We have a licensing system, Citrix ADM, hold the pool of capacity. This has a dual function in that it also provides a management overview, automation and config tracking of the appliances also. I posted an article about some of its benefits recently. The admin can then push changes for capacity from the management system or automate the whole process with some scripts. The automation could trigger on certain loads and then call off capacity as needed. This could free up the admin to work on other things.
We have the option to run ADM in this case as a cloud service, dropping the agents needed into each of the remote DC’s. This then simplifies the architecture by minimising the number of ports required to connect all this together.
Summary
Pooled capacity is a great option for managing Citrix ADC capacity, it provides flexibility should the need arise from the business and means that you can stay ahead of the game. Drop a note in the comments, I can talk about this all day(sad I know).