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From David McNelis <dmcne...@gmail.com>
Subject Re: cassandra 1.2.5- virtual nodes (num_token) pros/cons?
Date Fri, 26 Jul 2013 15:36:25 GMT
I second Romain, do the upgrade and make sure the health is good first.

If you have or plan to have a large number of nodes, you might consider
using fewer than 256 as your initial vnodes amount.  I think that number is
inflated from reasonable in the docs, as we've had some people talk about
potential performance degradation if you have a large number of nodes and a
very high number of vnodes, if I had it to do over again, I'd have done 64
vnodes as my default (across 20 nodes).

Another thing to be very cognizant of before shuffle is disk space.  You
*must* have less than 50% used in order to do the shuffle successfully
because no data is removed (cleaned) from a node during the shuffle process
and the shuffle process essentially doubles the amount of data until you're
able to run a clean.


On Fri, Jul 26, 2013 at 11:25 AM, Romain HARDOUIN <romain.hardouin@urssaf.fr
> wrote:

> Vnodes are a great feature. More nodes are involved during operations such
> as bootstrap, decommission, etc.
> DataStax documentation is definitely a must read.
> That said, If I were you, I'd wait somewhat before to shuffle the ring.
> I'd focus on cluster upgrade and monitoring the nodes. (number of files
> handles, memory usage, latency, etc).
> Upgrading from 0.8 to 1.2 can be tricky, there are so many changes since
> then. Be careful about compaction strategies you choose and double check
> the options.
>
> Regards,
> Romain
>
> rash aroskar <rashmi.aroskar@gmail.com> a écrit sur 25/07/2013 23:25:11 :
>
> > De : rash aroskar <rashmi.aroskar@gmail.com>
> > A : user@cassandra.apache.org,
> > Date : 25/07/2013 23:25
> > Objet : cassandra 1.2.5- virtual nodes (num_token) pros/cons?
> >
> > Hi,
> > I am upgrading my cassandra cluster from 0.8 to 1.2.5.
> > In cassandra 1.2.5 the 'num_token' attribute confuses me.
> > I understand that it distributes multiple tokens per node but I am
> > not clear how that is helpful for performance or load balancing. Can
> > anyone elaborate? has anyone used this feature  and knows its
> > advantages/disadvantages?
> >
> > Thanks,
> > Rashmi
>

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