Forgive me for being a shill, but InnoDB appears to have added a feature for the next release of the InnoDB plugin that prevents the buffer pool from getting wiped out by a full table scan. Many people have requested this. The documentation is excellent. I have tested it and not only did it work as advertised, but it didn't degrade performance on OLTP workloads. This fixes bug 45015 and is a nice feature to have when you occasionally use mysqldump to copy a table from a busy OLTP server. Now is a good time to evaluate MySQL 5.1 with the InnoDB plugin.