Apple’s upcoming release of OS X “Snow Leopard” has performance enhancements across the board for desktop users. Snow Leopard promises a more complete transition to 64 bit plus the ability to use graphics chips for traditional CPU operations. However, the server version of Snow Leopard also looks to provide huge performance gains and optimizations. Email, that basic service that every real server needs to offer, gets a huge leg up in Snow Leopard courtesy of a little open source project called Dovecot.
First released in 2002 by Timo Sirainen, a Finnish developer, Dovecot has slowly and silently improved email server performance on Unix and GNU/Linux systems. Savvy systems administrators started using Dovecot in place of traditional Unix email services to improve IMAP connectivity. While Dovecot can use the traditional “mbox” style of email storage, where each mailbox stores all messages in a single file, it shines when combined with the “Maildir” or “dbox” storage format, the latter being a Dovecot-only format.
“Maildir” and “dbox” allow for individual messages to reside in their own respective files. In a “Maildir” system, every message always has its own file. In a “dbox” system, Dovecot can intelligently allocate one or more messages to a respective file. This allows the email server to work with very large mailboxes, but without loading giant mailbox files into memory and then constantly stepping through them. Dovecot uses a high-performance index system to store and retrieve messages quickly. The results speak for themselves. Dovecot is fast. I’ve used it on servers for the past 2 years and going to Dovecot with “Maildir” storage increased email performance instantly. In addition, Dovecot’s compatibility with a lot of other email processing and filtering systems makes it ready for prime time.
By making Dovecot its default email service, Apple has once again innovated by utilizing great open source projects and integrating them into OS X. I can’t wait to see what else lands in the final version of OS X Snow Leopard server.
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