Riak CS need for 5 servers?

Shankar Dhanasekaran shankar at opendrops.com
Fri Apr 3 14:39:10 EDT 2015

Thanks for the links and additional explanation Chris. I will go through

One more question. My hosting provider sets a hard limit on the harddisk
size at the time of order. I go with, say, 20TB harddisk per server and
order 5 of them, I can get Riak running but I will still be limited to
20TB. If I need to increase my harddisk space, I would have to upgrade my
hardware that allows more disk bays. (limitation of my provider).

So if I needed to increase the capacity to, say, 60TB, will it work if I
add 5 more 60TB servers to the existing pool and decommission the old ones
after the data are replicated? How long does it take and how do I know the
replication is complete in the newly joined nodes?

On Fri, Apr 3, 2015 at 11:59 PM, Christopher Meiklejohn <
cmeiklejohn at basho.com> wrote:

> > On Apr 3, 2015, at 11:24 AM, Shankar Dhanasekaran <shankar at opendrops.com>
> wrote:
> >
> > Thanks Chris for your answer. I still don't comprehend what is meant by
> > this is the minimum amount of nodes needed to ensure all copies of each
> object are stored on different physical nodes. [2]
> >
> > Why can't a 3 node cluster store the data in each of them? I am reading
> the little riak book as well but still I don't understand what is the magic
> value of 5?
> Five is the minimum number of nodes required to guarantee each copy of
> each object is not stored on the same physical machine.  With three this
> can not be guaranteed, so you might have two copies (out of three) for a
> given object on the same machine.
> It’s an optimization problem computed during node membership referred to
> as “claim.”
> [1]
> http://lists.basho.com/pipermail/riak-users_lists.basho.com/2011-February/003319.html
> [2]
> http://basho.com/why-your-riak-cluster-should-have-at-least-five-nodes/
> Christopher Meiklejohn
> Senior Software Engineer
> Basho Technologies, Inc.
> cmeiklejohn at basho.com
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