[Dovecot] difference between client_limit and process_limit

Angel L. Mateo amateo at um.es
Mon Jun 11 13:19:39 EEST 2012

El 08/06/12 18:43, Timo Sirainen escribió:
> On 8.6.2012, at 19.33, Reindl Harald wrote:
>>> Yes, but like the wiki page also says, it's not a good idea increase client_limit for imap/pop3 processes.
>> depends on the usecase / workload
>> having dovecot as proxy for other imap-backends and 1 process per connection
>> will heavily raise up process-count and memory-overhead while memory
>> may be needed for the imap-backend (like dbmail) and datanases
>> process_limit                = 15
>> client_limit                 = 300
>> this way you can have 4500 proxy-connections and use most time
>> not more than 4-5 processes
> Proxying is done by imap-login process, not imap process. For login processes there are different recommendations.
	What are those recommendations? The ones at 

	Let's suppose... I have 4 mainly imap backend servers (but they admit 
also pop3 connections) with a process_limit of 5120 for service imap 
(and default_client_limit of 1000 applied to pop3). And I have 2 
director servers (configured as active-active behind a load balancer), 
so I need director servers to handle (more or less) 10240 imap connections.

	What is it better for the director's? Increasing process_limit for 
imap-login (so each process should handle less connections) or 
increasing client_limit (less processes handling more connections each)?

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