[Dovecot] Great time savings backing a mdbox versus Maildir

[Javier Miguel Rodríguez]

> So with mdbox disk I/O usage increased compared to maildir+ramdisk indexes?
>

     That is a "tricky" question to ask. It depends on usage, I think 
the following:


     - LDA delivery: load is a bit lower (on disk) in Maildir vs mdbox: 
in both cases the message has to be written, indexes are updated, in 
Maildir indexes are in ram, so lower "disk" load in this case

     - POP3 access: the same as the previous post

     - IMAP access: this is tricky. In mdbox a /"delete message"/ 
command only lowers the refcount, indexes are updated and in the night a 
cron job runs doveadm purge. In Maildir, you really delete the message 
when MUA/webmail /"compacts"/ the folder, and indexes are updated. I 
think that mdbox has a /"delayed IO" /in this case, and has less load on 
disk on "production hours".

     Am I missing anything? The stats in the SAN after the change 
maildir->mdbox do not help, we have zlib enabled in lda & imap with 
mdbox, so our # of real IOPs is lower than Maildir (we did not have zlib 
enabled)

     Regards

     Javier