One of our WP blogs was recently semi-slashdotted/neowinned and I've noticed something unfortunate - Apache 2 and MySQL 4.1 are extremely inefficient when compared to a site with very similar traffic using SQL Server 2000.
Roughly speaking, this WP blog has had about 200,000 hits in the past 24 hours. But this caused Apache 2 to steadily use about 60% of the server CPU resources, plus a chunk for MySQL 4.1. The IIS site, by comparison, get about 110,000 to 130,000 hits per day (on average), but IIS and SQL Server only use about 10% of the CPU.
I don't know how many queries the blog is making, but I suspect it's roughly the usual number between maybe 19 and 25. The IIS site makes 12 (mostly simple ones, granted).
So my question is: can WP be made more efficient? Is this what caching plugins fix/help? Why does it take 20 queries to display the home page? If the server was a Linux distro, would the speed be noticably better under this load?