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From Eric Gilmore <e...@datastax.com>
Subject Re: Node added, no performance boost -- are the tokens correct?
Date Fri, 01 Apr 2011 19:43:42 GMT
The DS docs go with "should" regarding setting the initial token to zero.
It's not a "must," but you get enough convenience out of never having to
move tokens on that node that I'm not sure why you wouldn't do it.

If anyone has a compelling reason not to do so, I'm happy to hear it :)

On Fri, Apr 1, 2011 at 10:58 AM, Edward Capriolo <edlinuxguru@gmail.com>wrote:

> On Fri, Apr 1, 2011 at 1:15 PM, Peter Schuller
> <peter.schuller@infidyne.com> wrote:
> >> Now, I moved the tokens. I still observe that read latency deteriorated
> with
> >> 3 machines vs original one. Replication factor is 1, Cassandra version
> 0.7.2
> >> (didn't have time to upgrade as I need results by this weekend).
> >
> > Read *latency* is fully expected to increase if you just add a node.
> > *Throughput* should increase, unless you have a workload that manages
> > to be more expensive on RPC than actual reads/writes.
> >
> > Latency would only be improved by additional nodes under some significant
> load.
> >
> > How are you benchmarking? Are you concurrently submitting requests to
> > all nodes at the same time? Try using stress.py from the Cassandra
> > tree as a comparison.
> >
> > If you're sending one request at a time, there is no expectation at
> > all of a performance improvement - just a decrease in performance.
> >
> > --
> > / Peter Schuller
> >
>
> To be clear on this issue. It does not matter where the tokens start
> it only matters that they are equally spaced around the token space.
>
> So for a 4 node clusters your tokens should either be
> 1 * ((2^127) / 4) = 42535295865117307932921825928971026432
> 2 * ((2^127) / 4) = 85070591730234615865843651857942052864
> 3 * ((2^127) / 4) = 127605887595351923798765477786913079296
> 4 * ((2^127) / 4) = 170141183460469231731687303715884105728
>
> or
> 0 * ((2^127) / 4) = 0
> 1 * ((2^127) / 4) = 42535295865117307932921825928971026432
> 2 * ((2^127) / 4) = 85070591730234615865843651857942052864
> 3 * ((2^127) / 4) = 127605887595351923798765477786913079296
>
> If you move one you have to move the rest because the distance between
> 170141183460469231731687303715884105728 and 0 is 1
>

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