Transaction logs can be kept on a physical drive that is separate from their respective .edb files. However, by default, information store logs are maintained in the Exchsrvr\Mdbdata directory and directory service logs are maintained in the Exchsrvr\Dsadata directory.
Each subdirectory contains an Edb.log file, which is the current transaction log file for the respective service. Both the information store subdirectory and the directory service subdirectories maintain separate Edb.log files. Log files should always be 5,242,880 bytes in size; if the are not this size, they are probably damaged.
Because transactions are first written to the Edb.log files and then written to the database, the current actual or effective database is a combination of the uncommitted transactions in the transaction log file, which alo reside in memory, and the actual .edb database file.