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From Edward Capriolo <edlinuxg...@gmail.com>
Subject Re: has anyone used dynamic snitch at all
Date Fri, 08 Mar 2013 19:40:18 GMT
dynamic_snitch=true is the default. So it is usually on "wrapping" other
snitches. I have found several scenarios where it does not work exactly as
your would expect.

On Fri, Mar 8, 2013 at 2:26 PM, Hiller, Dean <Dean.Hiller@nrel.gov> wrote:

> Our test setup
>
> 4 nodes, RF=3, reads at CL=QUOROM and we tried CL=TWO
> Tell the network card to slow down every packet on node 2
> After fixing astyanax to not go to node 2 anymore, we are still seeing
> cassandra have issues as it seems to be involving node 2 somehow.  If we
> take node 2 down, it all speeds back up.
>
> We are trying to get this working such that a slow node in cassandra does
> not impact our customers.
>
> We are in 1.2.2 and added the following properties….(our properties show
> PropertyFileSnitch though I see the keyspace has
> org.apache.cassandra.locator.SimpleStrategy set probably because it was
> created through a tool instead of CLI…shucks)….anyways, I still expected
> dynamic snitch to work….
>
> # controls how often to perform the more expensive part of host score
> # calculation
> dynamic_snitch: true
> dynamic_snitch_update_interval_in_ms: 100
> # controls how often to reset all host scores, allowing a bad host to
> # possibly recover
> dynamic_snitch_reset_interval_in_ms: 600000
> # if set greater than zero and read_repair_chance is < 1.0, this will allow
> # 'pinning' of replicas to hosts in order to increase cache capacity.
> # The badness threshold will control how much worse the pinned host has to
> be
> # before the dynamic snitch will prefer other replicas over it.  This is
> # expressed as a double which represents a percentage.  Thus, a value of
> # 0.2 means Cassandra would continue to prefer the static snitch values
> # until the pinned host was 20% worse than the fastest.
> dynamic_snitch_badness_threshold: 0.1
>
> Any help appreciated,
> Thanks,
> Dean
>

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