dovecot - Jun 2010 - auth_cache_size

I was going to ask how much space I should allocate for auth_cache_size 
- but decided to read the wiki first.  Now I'll be more specific -

Wiki says about 50 bytes per passdb, and up to 200 bytes for userdb - so 
my arithmetic says each combined entry needs 250 bytes budgeted.  
Assuming that's correct, I need some clarification.

Let's start small.  Assume ten users, all connected - and everybody also 
likes looking at everybody else's mailbox.  So there are ten clients, 
each with at least ten connections (I say at least because each folder 
viewed within an account is its own connection, right?).

How is the auth_cache used?  If I have ten user/pass combinations - is 
that all that is stored?  Or are there connection-specific entries as 
well?  In other words, for the above example, do I have 10 x 250 bytes 
yields auth_cache_size=3, or do I need 10 x 10 x 250 yields 
auth_cache_size=30 - or am I totally off?
-- 
Daniel

On Fri, 2010-06-25 at 08:09 -0700, Daniel L. Miller
wrote:
> Let's start small.  Assume ten users, all connected - and everybody
also
> likes looking at everybody else's mailbox.  So there are ten clients, 
> each with at least ten connections (I say at least because each folder 
> viewed within an account is its own connection, right?).
> 
> How is the auth_cache used?  If I have ten user/pass combinations - is 
> that all that is stored?
It caches passdb and userdb lookups+replies. Both are independent of
each others.
> Or are there connection-specific entries as well?
No.
> In other words, for the above example, do I have 10 x 250 bytes 
> yields auth_cache_size=3, or do I need 10 x 10 x 250 yields 
> auth_cache_size=30 - or am I totally off?
10 x 250. But negative hits ("user not found") are also cached (unless
you disable them) and they can also increase the cache usage.