Why not to compress SQL Server data and log files

Very interesting explanation about why you shouldn't compress SQL Server log files and database files at http://blogs.msdn.com/khen1234/archive/2005/04/25/411852.aspx.

The obvious answer is performance, of course, but why performance suffers in this scenario is rather interesting. It's more than just the hit of compressing and decompressing the database data and log files. In short, when a compressed file is being read from or written to, IO operations are ALWAYS run synchronously.