joel spolsky

I love stories about performance problems. Recently, my friend Debra Lilley sent me this one:

I went to see a very large publishing company about 6 months after they went live. I asked them what their biggest issue was, and they told me querying in GL was very slow, and I was able to fix quite easily. (There was a very simple concatenated index trick for the Chart of Accounts segments that people just never used.) Then I asked if there was anything else. The manager said no but the clerk who sat behind him said, “I have a problem.” His manager seemed embarrassed, but when I pressed him, the clerk continued, “Every day I throw away reams of paper from our invoice listing.”

Joel Spolsky's article on Solid State Disks is a great example of a type of problem my career is dedicated to helping people avoid. Here's what Joel did:

1. He identified a task needing performance improvement: "compiling is too slow."
2. He hypothesized that converting from spinning rust disk drives (thanks mwf) to solid state, flash hard drives would improve performance of compiling. (Note here that Joel stated that his "goal was to try spending money, which is plentiful, before [he] spent developer time, which is scarce.")
3. So he spent some money (which is, um, plentiful) and some of his own time (which is apparently less scarce than that of his developers) replacing a couple of hard drives with SSD. If you follow his Twitter stream, you can see that he started on it 3/25 12:15p and wrote about having finished at 3/27 2:52p.
4. He was pleased with how much faster the machines were in general, but he was disappointed that his compile times underwent no material performance improvement.

Here's where Method R could have helped. Had he profiled his compile times to see where the time was being spent, he would have known before the upgrade that SSD was not going to improve response time. Given his results, his profile for compiling must have looked like this:

100%  Not disk I/O
 0%  Disk I/O
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