[Dovecot] IMAP-proxy or not with sogo webmail and dovecot backend

Ed W lists at wildgooses.com
Wed Feb 22 11:31:55 EET 2012

On 22/02/2012 08:25, Jan-Frode Myklebust wrote:
> On Tue, Feb 21, 2012 at 02:33:24PM +0000, Ed W wrote:
>> I think the original question was still sensible.  In your case it
>> seems like the ping times are identical between:
>>      webmail ->  imap-proxy
>>      webmail ->  imap server
>> I think your results show that a proxy has little (or negative)
>> benefit in this situation, but it seems feasible that a proxy could
>> eliminate several RTT trips in the event that the proxy is "closer"
>> than the imap server?  This might happen if say the imap server is
>> in a different datacenter (webmail on an office server machine?)
> The webmail/imapproxy were actually running in a different datacenter to
> the dovecot director/backend servers, but only about 20KM away.
> Ping tests:
> webmail->director:
> 	rtt min/avg/max/mdev = 0.933/1.061/2.034/0.183 ms
> director->backend:
> 	rtt min/avg/max/mdev = 0.104/0.108/0.127/0.005 ms
> webmail->localhost:
> 	rtt min/avg/max/mdev = 0.020/0.062/1.866/0.257 ms
>    -jf

Hmm, not sure I understand the original numbers then?

It seems intuitive that the proxy installed locally could save you 2x 
RTT increment, which is about 0.8ms in your case.  So I might expect the 
proxy to reduce rendering times by around 1.6ms simply because it 
reduces the number of round trips to login?  Kind of curious why that's 
not achieved..?


Ed W

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