Dovecot performance tuning ========================== Disk I/O optimization --------------------- Usually heavily loaded IMAP and POP3 servers don't use much CPU, but they use all the disk I/O they can get. So reducing disk I/O is probably the most useful optimization you can do. * See for generic disk I/O optimizations. * See for mbox-specific optimizations. * See for Maildir-specific optimizations. * See [MailboxFormat.dbox.txt] for Dovecot's own high-performance mailbox format. It usually gives much better performance than mbox/Maildir. * See [Plugins.FTS.txt] for optimizing IMAP SEARCH command. * See for POP3 optimizations, especially 'pop3_no_flag_updates=yes' CPU usage optimization ---------------------- * See for optimizing CPU usage caused by logins * See 'auth_cache_size' setting for caching passdb and userdb lookups * Services having client_limit>1 and process_limit>1, set process_min_avail to the number of CPU cores * To reduce forks by reusing existing processes for new requests increase 'service { service_count }' from 1 to higher (e.g. 100) for imap and pop3 services. It's better not to set it too high or unlimited (0), because different users use different amounts of memory, and it's wasteful when a lot of processes end up having a lot of "free" memory. Memory usage optimization ------------------------- There aren't many settings which affect Dovecot's memory usage. About the only such settings are 'auth_cache_size' and settings. In general Dovecot uses as much memory as it needs, which is usually quite little. Note that these settings do not directly affect the memory usage: * 'service { vsz_limit } ': These are simply safe guards against potential memory leaks. If the process's virtual size reaches the limit, the process is killed by the kernel. * 'service { process_limit, client_limit } ': These are mostly to avoid DoS attacks using up all your memory. (This file was created from the wiki on 2013-11-24 04:42)