Keeping Data on N Separate Physical Computers

Alexander Sicular siculars at gmail.com
Thu Feb 24 08:56:21 EST 2011


I believe in a three node cluster your replicas are algorithmically guaranteed to be on two nodes. I think it is something like p=n-1. Where p is physical machines and n are replicas.

On Feb 24, 2011, at 6:44 AM, Runar Jordahl wrote:

> As far as I understand you need to buy Riak EnterpriseDS to have any
> guarantee for durability & availability for data you store in Riak:
> 
> “There are no guarantees that the (…) replicas will go to (N) separate
> physical nodes; however, the built-in functions for determining where
> replicas go attempts to distribute the data evenly."
> 
> http://wiki.basho.com/Replication.html#So-what-does-N%3D3-really-mean%3F
> 
> 
> Basically, whatever N you set, they might end up on the same hard
> disk, meaning that one hard disk crash can mean you lose data and/or
> make data not readable. Probability is low, but it can happen.
> 
> Am I correct?
> 
> Kind regards
> Runar
> 
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