Hi Mahadev,

It lets one run multiple 2-node clusters. Suppose I have an application that
does a simple 2-way mirroring of my data and uses ZK for clustering. If I
need to support many 2-node clusters, where will I find the spare machines
to run the third instance for each cluster?

-Vishal

On Mon, Oct 25, 2010 at 5:14 PM, Mahadev Konar <maha...@yahoo-inc.com>wrote:

> Hi Vishal,
>  This idea  (2.) had been kicked around intially by Flavio. I think heĀ¹ll
> probably chip in on the discussion. I am just curious on the whats the idea
> behind your proposal? Is this to provide some kind of failure gaurantees
> between a 2 node and 3 node cluster?
>
> Thanks
> mahadev
>
> On 10/25/10 1:05 PM, "Vishal K" <vishalm...@gmail.com> wrote:
>
> > Hi All,
> >
> > I am thinking about the choices one would have to support multiple 2-node
> > clusters. Assume that for some reason one needs to support multiple
> 2-node
> > clusters.
> > This would mean they will have to figure out a way to run a third
> instance
> > of ZK server for each cluster somewhere to ensure that a ZK cluster is
> > available after a failure.
> >
> > This works well if we have to run one or two 2-node clusters. However,
> what
> > if we have to run many 2-node clusters?
> >
> > I have following options:
> > 1. Find m machines to run the third instance of each cluster. Run n/m
> > instances of ZK on each machine.
> > 2. Modify ZooKeeper server to participate in multiple clusters. This will
> > allow us to run y instances of third node where each instance will be
> part
> > of n/y clusters.
> > 3. Run the third instance of ZK server required for the ith cluster on
> one
> > of the server on (i+1)%n cluster. Essentially, distribute the third
> instance
> > across the other clusters.
> >
> > The pros and cons of each approach are fairly obvious. While I prefer the
> > third approach, I would like to check what everyone thinks about the
> second
> > approach.
> >
> > Thanks.
> > -Vishal
> >
>
>

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