It is a known fact that ext3 is not the most efficient file system out there and for example file removals can be painfully slow and cause a lot of random I/O. However, as it turns out, it can sometimes have a much more severe impact on the MySQL performance that it would seem. When or why?

When you run DROP TABLE there are several things that need to happen – write lock on a table so it cannot be used by any other thread, the data file(s) removal by the storage engine and of course in the end MySQL has to destroy the definition file (.frm). That's not all that happens, there is one other thing:

CODE:
 

VOID(pthread_mutex_lock(&LOCK_open)); 
error= mysql_rm_table_part2(thd, tables, if_exists, drop_temporary, 0, 0); 
pthread_mutex_unlock(&LOCK_open);