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From Eric Evans <eev...@rackspace.com>
Subject Re: Performance with Multiple Node Vs Single Node
Date Thu, 18 Feb 2010 16:04:41 GMT
On Thu, 2010-02-18 at 17:36 +0200, Richard Grossman wrote:
> What the impact on performance to have multiple node ??

When you have a cluster with only one node, you're guaranteed to perform
every read and write on the destination node (because there is literally
no other possible destination). When you have multiple nodes, you can
read/write to any node, but if it is not the destination, then it must
be forwarded on to the right host. So the expected impact on performance
is the extra latency incurred by these forwarded requests.

> The test we run here with multiple node seems a VERY bad performance
> comparing to the same amount of data located on 1 single node.
> Could you confirm or infirm such statement ?
> 
> I mean if the same operation (write or read) take 5-10 times more time
> when multiple node than single node where is the problem
> (communication between computer) ??. 

5-10 times more is not normal, no. Perhaps there is a problem with one
or more of the new nodes you added.

> I've read a lot about tuning of memory, disk, io, top, htop but
> nothing about networking operation between node. Is there any way to
> check what going on regarding node intercommunication ??

I'd start with your basic, garden-variety troubleshooting, i.e. ping,
traceroute, transfer speed, etc.
 
-- 
Eric Evans
eevans@rackspace.com


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