Large ring_creation_size

Greg Nelson grourk at dropcam.com
Wed Apr 13 17:11:14 EDT 2011


Ok, how about in this case I described? It runs out of memory with a single pair of nodes...

(Or did you mean there's a connection between each pair of vnodes?)
On Wednesday, April 13, 2011 at 1:56 PM, Jon Meredith wrote:
Hi Greg et al,
> 
> As you say largest known is not largest possible. Internally within Basho, the largest cluster we've experimented with so far had 50 nodes.
> 
> Going beyond that it's speculation from me about pain points. 
> 
> 1) It is true that you need enough file descriptors to start up all partitions when a node restarts - Riak checks if there is any handoff data pending for each partition. We have work scheduled to address that in the medium term. The plan is to only spin up partitions the node owns and any that have been started as fallbacks that handoff has not completed for. Until that work is done you will need a high ulimit with large ring sizes. 
> 
> 2) It is also true that Erlang runs a fully connected network, so there will be connections between each node pair in the cluster. We haven't determined the point at which it becomes a problem. 
> 
> So it looks like you'll be pushing the known limits. Basho will do our very best to help overcome any obstacles as you encounter them.
> 
> Jon Meredith
> Basho Technologies.
> 
> On Wed, Apr 13, 2011 at 1:41 PM, Greg Nelson <grourk at dropcam.com> wrote:
> > The largest known riak cluster != the largest possible riak cluster. ;-)
> > 
> > The inter node communication of the cluster depends on the data set and usage pattern, doesn't it? Or is there some constant overhead that tops out at a few hundred nodes? I should point out that we'll have big data, but not a huge number of keys. 
> > 
> > The number of vnodes in the cluster should be equal to the ring_creation_size under normal circumstances, shouldn't it? So when I have a one node cluster, that node is running ring_creation_size vnodes... File descriptors probably isn't a problem -- these machines won't be doing anything else, and the limits are set to 65536. 
> > 
> > Thinking about the internode communication you mentioned, that's probably where the resource hog is.. socket buffers, etc.
> > 
> > Anyway, I'd also love to hear more from basho. :)
> > On Wednesday, April 13, 2011 at 12:33 PM, siculars at gmail.com wrote:
> > > Ill just chime in and say that this is not practical for a few reasons. The largest known riak cluster has like 50 or 60 nodes. Afaik, inter node communication of erlang clusters top out at a few hundred nodes. I'm also under the impression that each physical node has to have enough file descriptors to accommodate every virtual node in the cluster. 
> > > 
> > > I'd love to hear more from basho. 
> > > 
> > > -alexander 
> > > 
> > > 
> > > Sent from my Verizon Wireless BlackBerry
> > > 
> > > -----Original Message-----
> > > From: Greg Nelson <grourk at dropcam.com>
> > >  Sender: riak-users-bounces at lists.basho.com
> > > Date: Wed, 13 Apr 2011 12:13:34 
> > > To: <riak-users at lists.basho.com>
> > >  Subject: Large ring_creation_size
> > > 
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