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

[Ed W]

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..?

Cheers

Ed W