It depends how many SSDs you need. If you have one hard disk that needs to be upgraded to an SSD, do that instead of spending developer time on it. However, if you have thousands of disks that would all need to be upgraded to SSDs to save your 20%, it might be worth looking into software optimization.
Same for manual cleanups and stuff. If you need to fix half a dozen source files, just wince and do it manually. If you need to fix thousands of source files, it's probably time to write a parser & refactoring browser and then use that.
> However, if you have thousands of disks that would all
> need to be upgraded to SSDs to save your 20%, it might be
> worth looking into software optimization.
However the margin is still quite high. I've replaced twice big EMC SAN arrays with 8 SSDs, and the performance gain was 300 to 400% (different customers, different applications).
SSDs envelope is usually quite narrow, but if you hit the sweet spot it's such a game changer than it beats everything else.
Same for manual cleanups and stuff. If you need to fix half a dozen source files, just wince and do it manually. If you need to fix thousands of source files, it's probably time to write a parser & refactoring browser and then use that.