(Originally posted 2011-08-12.)
In WLM Velocity – "Rhetorical Devices Are Us"
I mentioned a graph I wasn’t going to publish – essentially to protect a customer. In this post I’m again going to describe a graph I have (at least in my head) without publishing it. (And for essentially the same reasons.) I hope you find it useful, however:
I’ve been acquainted with a lot of customer Batch Window Reduction projects, especially in the past two years. When I hear of a new one I "plot" the situation on the "graph in my head". So, if I tell you that what you’re trying to do is likely to succeed (or conversely that it isn’t) that’s (mostly) where it’s coming from.
So, about that graph:
- On the x axis I plot the degree of scale up you’re trying to achieve. So, I might talk about "2X" or "1.3X".
- On the y axis I plot how much time you have to achieve that in. Which might be as little as "by next month end" (no really!) or "within the next 2 years".
You can probably guess what’s coming next:
If you are trying to achieve a big scale up (say 5X, to quote a real recent case) in not much time (say 3 months, thankfully not the same case but nonetheless a real value) then I’d classify that as very high risk. (That’s the bottom right hand corner of the graph.)
On the other hand 1.3X in 2 years is very low risk and is in the top left hand corner of the graph. (I’ve never seen anyone that lucky.)
So that’s the graph – just another rhetorical device. But there are some wrinkles. I’ll list a few – and you can probably think of a few more:
- What if we have "way points"? Say 1.5X in 6 months and 2X in a year?
- By which metric is it, say, 2X?
- This says nothing about cost. Zero cost probably means zero speed up. Infinite cost might make the batch go a lot faster.
- This doesn’t speak to efforts already undertaken. Obviously a thoroughly-well-tuned application is unlikely to speed up as much as an untuned one.
For these reasons I wouldn’t take the graph too seriously and I don’t entirely rely on it. It’s also a part of why I’m leery of committing to precise speed-up numbers.
Being a Performance person I hope any fuzz in my language reflects the fuzz in the situation, not a general unwillingness to commit. If you think I’m doing the latter be sure to tell me so.
In the meantime I hope you find this rhetorical device useful.