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Re: [Dovecot] IMAP-proxy or not with sogo webmail and dovecot backend Ed W Wed Feb 22 02:00:38 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..?

Cheers

Ed W