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From aaron morton <aa...@thelastpickle.com>
Subject Re: Optimizing a few nodes to handle all client connections?
Date Sun, 20 Mar 2011 22:37:15 GMT
ah, my flippant comments at the end. 

Instead of "Single point of failure" perhaps I should have said "specialist nodes are a bad
idea as they may reduce the overall availability of the cluster to the availability any one
sub group." e.g. a cluster of 10 nodes, where 8 are data and 2 are connections may be down
for 100% of the keys after the loss of 2 nodes if they happen to be the connection nodes.
 

WRT the partitioner I was thinking of a situation such as 

node 1 : 33.3% of the ring
node 2 : 33.3% of the ring
node 3 : 33.3% of the ring
node 4 : 0.1% of the ring 

My point was that giving the node a small token range would not be enough to reduce it's data
load. If node 4 was a functioning node in the ring then at RF 3 it will be asked to be a replica
for the data from nodes 2 and 3. Unless the replica strategy excluded the node from the list
of natural endpoints for all but the token range it was responsible for. 

Aaron


On 21 Mar 2011, at 10:28, Robert Coli wrote:

> On Sun, Mar 20, 2011 at 1:20 PM, aaron morton <aaron@thelastpickle.com> wrote:
>> Even if the node is only
>> responsible for a small about of the ring, it would normally still get data
>> handed to it and read from it as a replica. You would need to use a Replica
>> Placement Strategy that knew it ignore the "connection only" nodes.
>> IMHO it's a bad idea: Single point of failure, wasted compute resources,
>> imbalance between "connection" and "worker" nodes.
> 
> As I understand what is being proposed, the node could only be
> responsible for a single token, and presumably would perform very well
> indeed when reading or writing that token. I don't see why you would
> need to avoid placing a single token's worth of data on a node, or why
> it would become a single point of failure if you did.. is there
> something I'm missing.. ?
> 
> =Rob


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