Exchange writes all transactions first to the current transaction log file. Thus, the current database encompasses the uncommitted data in the transaction log and the .edb database file.

Always place log files on a separate disk from the .edb files, for two reasons. First, you can increase performance significantly—by 30 percent or more—by placing the .log files away from the .edb files. Second, the chances of recovering from a system meltdown increase when .log files are separate from .edb files. For example, if the hard disk where you store the Exchange databases suddenly fails, you can rebuild the .edb files to their state before the crash if the .log files are still available on the other good partition.

You can move transaction log files to other partitions in two ways. The easiest way is to use the Performance Optimizer, shown in Screen A, which automatically determines whether you can separate the transaction logs from the databases. You can run the Performance Optimizer (from Start, Programs, Exchange, Exchange Optimizer) during the Exchange setup process or any time thereafter.

You can move the log files (or database files) manually by choosing an alternative drive for file storage from the Database Paths tab on the server's Properties sheet. The Performance Optimizer is the better tool, because it automatically stops and starts the services for you.