What's a Reasonable Inbox Size?

[Joseph Tam]

On Fri, 8 May 2020, Joseph Tam wrote:

>>> It depends on what you consider reasonable.

Whoops.  Editing error.  What I wanted to send.

On Fri, 8 May 2020, asai at globalchangemusic.org wrote:

> So, generally speaking, you don't want to have inboxes that just sync all day 
> long, due to massive amounts of small files in the inbox.

I don't know enough about what is involved when your client tries
to sync to comment on your particular situation.  If the exchange of
information involves only delta changes (e.g. list datum that have been
added/removed since the last sync), and if this information is readily
available in Dovecot's caches, then this operation might be optimized
to take minimal time.

If however, it involves exchanging entire lists of many messages IDs,
or worse, involves Dovecot accessing each message, it will result in
large amounts of time spent in I/O (network, disk or both).  With Maildir
(many small message in a folder), this causes seeking all over the disk.
Some filesystems (XFS?) may be better at this than others.

The description of your problem seems to suggest the latter, so breaking
up gigantic mailboxes into manageable volumes will help.

If you really want to see what's going on when a client syncs, you
can network trace, process trace, or use Dovecot's rawlog feature

 	https://wiki.dovecot.org/Debugging/Rawlog

to directly observe the iteraction between a server and client.

> This may be OK in the case of a rarely accessed archive folder, but not
> good for regularly accessed inboxes, etc.?

This is not really so much technical advice as a rule of thumb: there's
not a lot of payoff to optimizing rare operations.

Joseph Tam <jtam.home at gmail.com>