Okay so it's time for a rant. One of the common performance scenarios we face often relates to comparative performance, i.e. this system used to run at X/sec, now it runs at Y/sec, or alternatively, host A is processing N ops/sec where host B is at M ops/sec, but they are identical systems.
Oh really?
If there is a difference in performance, then they are *NOT THE SAME*. Period.
This is just logic, folks. You might not know where the differences are, but they are still there.
My point here, is that I often have to deal with people telling me that no changes have been made to a system, or that 2 hosts are identical, yet they are seeing a performance degradation. By denying a change or difference (and it's common for people to refuse or avoid investigating in this direction) you are specifically avoiding the area where the problem must lie!
Now, such a difference could be a very subtle thing, such as load pattern, number of users, timings, etc, rather than an obvious patch/upgrade/whatever. There is often resistance investigating the actual workload characteristics because most people simply don't know, and it can be a lot of work to find out if the end user has no handle on what their systems are doing. They want the magic bullet that will just make things go faster, but without an understanding of the workload you're guessing at best. Starting off an investigation from the right mindset makes all the difference, and as I've said already on this blog - context is critical, otherwise performance statistics are just numbers.
I feel better now.
Oh really?
If there is a difference in performance, then they are *NOT THE SAME*. Period.
This is just logic, folks. You might not know where the differences are, but they are still there.
My point here, is that I often have to deal with people telling me that no changes have been made to a system, or that 2 hosts are identical, yet they are seeing a performance degradation. By denying a change or difference (and it's common for people to refuse or avoid investigating in this direction) you are specifically avoiding the area where the problem must lie!
Now, such a difference could be a very subtle thing, such as load pattern, number of users, timings, etc, rather than an obvious patch/upgrade/whatever. There is often resistance investigating the actual workload characteristics because most people simply don't know, and it can be a lot of work to find out if the end user has no handle on what their systems are doing. They want the magic bullet that will just make things go faster, but without an understanding of the workload you're guessing at best. Starting off an investigation from the right mindset makes all the difference, and as I've said already on this blog - context is critical, otherwise performance statistics are just numbers.
I feel better now.
