poor update perfomance

[alix jermyn]

I am using MySql 4.1.7 on a 3GHz windows XP machine.

On the same machine I have a Java Application which loads a simple (indexed, MyIsam) table from the db into an in memory Java cache which uses the db as persistent backing. For this application, there is likely to be around 100 updates for each insert.

For table sizes of up to 200k records, I can write about 3.0 - 4.0k updates per second back to the table via jdbc.

When I run the identical tests with the table at 2.5M rows, get consistently max out at about 100 updates every 5 to 6 seconds, some 200 times slower than with the table at 200k.

I'm a Java guy with a reasonable amount of db experience, but not much MySql experience - any suggestions or perfomance advice.