[Pgcluster-general] slow data-read performances

[Julien Garet]

Filip Rembiałkowski wrote:
> 2008/8/18 Julien Garet <Julien.Garet at inria.fr>:
>   
>> Hi,
>>
>>   I've just setup a testing cluster of postgresql with pglcuster and there
>> is something and do understand with the perfs. My setup is quite simple, I
>> have two identical boxes with database and replicator under centos 5, it
>> works well. I have done some testing  with pgbench and a third identical box
>> running postgres 8.3 without postgres as reference.
>>    The number of tps is about 5 times less in the cluster compared to the
>> reference box, using all kind of queries of pgbench (1 select, 1 insert et 3
>> update), which is quite normal, due to the overhead of the cluster in
>> writing data. But when I use pgbench, only using select queries, the nodes
>> of the cluster are still 5 times slower than the reference postgresql
>> server. And I don't understand that as pgcluster isn't supposed to replicate
>> data-read queries between nodes, the data-read performances should be the
>> same as the reference. Are there any clues to this mysterious thing ?
>>
>>     
>
> Hello
>
> How many client connections are you using?
>   
I am using 16 clients
> Are you connecting to pglb? If you connect to one of cluster dbs there
> will be no load balancing.
>   
I am not, I use a cisco load balancer (as I believe load balancing is a 
network matter, not a software thing ;-)) I have run pgbench on all the 
nodes + the load balanced IP.
> Can you email pgbench commandline and results here?
>   
see attached document. node1 and node2 are the nodes of the cluster, slb 
is the load balanced address (which forward requests to the two nodes 
with a least connection algorithm), ref the reference postgresql server.
>
> regards
>
>
>
>   
thanks for your help

-- 
Cordialement,

Julien Garet
Service des Moyens Informatiques
INRIA - Lille Nord Europe
Parc Scientifique de la Haute Borne
40, avenue Halley
59650 Villeneuve d'Ascq
Tél : 03.59.57.78.28

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