[imp] Horde/IMP performance problems

[Michael Menge]

Quoting Jochen Roderburg <Roderburg at Uni-Koeln.DE>:

> Zitat von Michael Menge <michael.menge at zdv.uni-tuebingen.de>:
>
>> We are running a HA/LB cluster of two servers (2x quadcore XEON E5420
>> 2,5GHz, 16 GB ram each)
>>
>> ClusterIP is used to distribute the load between the servers.
>> - eAccelerator to speed up php,
>> - Memcache for caching,
>> - tempfs and Memcache for Sessions.
>> - PgPool is used to keep the two PostgreSQL databases in sync,
>>  it will eat up most of the performance gained by the second server,
>>  but removes the single point of failure.
>
> So even after all this tuning a single machine was not enough for the load?

A single machine would have worked for the moment, but we wouldn't have
much recources left to grow and we wouldn't have a HA system.

> The idea came also already up here to use more machines with load balancing.
> Is this easily possible with Horde?
> ClusterIP is the additional software you need for this?

As http/https don't use persitant connections, but the client expects  
to continue at the same point you have to share all informations  
(session, cache, database) between the servers or ensure that the  
client connects to the same server.

As we couldn't find a HA and fast system to ensure shared sessions and cache.
We went the second way. Both servers share one IP-Adress. ClusterIP is  
a iptables rule which distrubutes the clients to the servers.

http://security.maruhn.com/iptables-tutorial/x8906.html
(we use --hashmode sourceip as other hashmodes will not ensure that
the same client will connect to the same server)

If the client-ip changes (e.g. DSL-reconcect / DNS Roundrobin webproxys)
it can happen that the client will be connect to an other server and
must login again, as the sessions are shared between servers.


> Does this work with SSL?
>

Yes. But both servers should have the same Certs/Keys

> Best regards,
> Jochen Roderburg
>
>
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--------------------------------------------------------------------------------
M.Menge                                Tel.: (49) 7071/29-70316
Universität Tübingen                   Fax.: (49) 7071/29-5912
Zentrum für Datenverarbeitung          mail:  
michael.menge at zdv.uni-tuebingen.de
Wächterstraße 76
72074 Tübingen
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