sendmail Performance Tuning

3.6. Summary

• Most email servers end up being I/O bound. On email gateways, the primary source of I/O contention involves the mail queue.

• Email I/O is (1) write-intensive, (2) synchronous, and (3) characterized by small and random accesses. Using a high-performance filesystem that gracefully handles directories with many entries and efficiently but safely handles synchronous writes can be an enormous win.

• Storage space rarely emerges as an issue in an email queue unless something goes wrong. A disk’s suitability for this purpose should be determined by how many operations per second it can perform.

• For email performance, we’re primarily interested in increasing the amount of email that can be moved on and off a machine per unit time. While the latency ...