Performance is one of the major concerns in the cloud. But the question should not really be whether or not the cloud performs, but whether the Application in question can and does perform in the cloud. The main problem here is that application performance is either not managed at all or managed incorrectly and therefore this question often remains unanswered. Now granted, performance management in cloud environments is harder than in physical ones, but it can be argued that it is easier in public clouds than in on-premise clouds or even a large virtualized environment. How do I come to that conclusion? Before answering that let’s look at the unique challenges that virtualization in general – and clouds in particular – pose to the realm of APM.

Time is relative

The problem with timekeeping is well known in the VMWare community. There is a very good VMWare whitepaper that explains this in quite some detail. It doesn’t tell the whole story, however, because obviously there are other virtualization solutions like Xen, KVM, Hyper-V and more. All of them solve this problem differently. On top of that the various guest operating systems behave very differently as well. In fact I might write a whole article just about that, but the net result is that time measurement inside a guest is not accurate, unless you know what you do. It might lag behind real time and speedup to catch up in the next moment. If your monitoring tool is aware of that and supports native timing calls it can work around that and give you real response times. Unfortunately that leads to yet another problem. Your VM is not running all the time, like a process it will get de-scheduled from time to time; however, unlike a process it will not be aware of that. While real time is important for response time, it will screw with your performance analysis on a deeper level.

Continue reading the full blog by Michael Kopp


Not Logged In? Customers and AJAX Edition Users Login with your Community Account