I would *strongly* recommend against upgrading from 0.8 directly to 1.2. 
Skipping a major version is generally not recommended, skipped 3 would seem 
like carelessness. 

> I second Romain, do the upgrade and make sure the health is good first.
+1 but I would also recommend deciding if you actually need to use virtual 
nodes. The shuffle process can take a long time and people have had mixed 
experiences with it. 

If you wanted to move to 1.2 and get vNodes I would consider spinning up a new 
cluster and bulk loading into it. You could do an initial load and then to 
delta loads using snapshots, there would however be a period of stale data in 
the new cluster until the last delta snapshot is loaded. 

Cheers

-----------------
Aaron Morton
Cassandra Consultant
New Zealand

@aaronmorton
http://www.thelastpickle.com

On 27/07/2013, at 3:36 AM, David McNelis <dmcne...@gmail.com> wrote:

> 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.hardo...@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.aros...@gmail.com> a écrit sur 25/07/2013 23:25:11 :
> 
> > De : rash aroskar <rashmi.aros...@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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