sendmail Performance Tuning

4.3. Storage Systems

Compared to most common file benchmarks, the I/O operation mix that typically takes place in email message stores is write-heavy, synchronous, and nonsequential, just as it is in the queue. Disks spend a lot of time writing data to random locations in the message store, and modifications to these files are followed by fsync()s. Unlike in the mail queue, however, file creates in the message store are less likely to be followed by immediate deletes. Files in the message store are significantly less temporary. Further, the amount of storage required in the message store is at least one and probably two or more orders of magnitude larger than space in the queue. For any performance-sensitive email system, use of a Redundant ...