On 18.3.2012, at 0.28, Sven Hartge wrote: > mbox has big problems with concurrent writes, the bigger the mbox is, > the more problems you get. This is mainly caused by the meta-data of a > message (meaning flags, status, etc.) which is stored inside the mbox > file itself. Flagging a message as read or replied causes the whole mbox > file to be rewritten.
Dovecot moves only minimal amount of data within mbox. A flag change writes only a few bytes to mbox file, it doesn't rewrite it the whole file. Only time when the entire mbox file is rewritten is when you expunge the first message.
