Hi Ector,
*RAID 1 would cut your per node disk capacity in half (1.5TB), so at 4 nodes, your overall cluster capacity would only be 6TB.* As I mentioned every server has two 3TB HDD (total 6TB), so the cluster size would effectively be 12TB in a Raid 1 configuration. The biggest issue here is that with both Raid 1 and a replication factor of 2, every piece of data is going to be stored four times the cluster. Another solution could be a replication factor of 2 with Raid 0. If an HDD fails I will lose the machine, but I can safely bring it up again since the data has been already stored in the other nodes. On Thu, Feb 27, 2014 at 6:18 AM, Hector Castro <[email protected]> wrote: > Hi Marco, > > Please see my responses inline below. > > -- > Hector > > > On Thu, Feb 27, 2014 at 3:04 AM, Marco <[email protected]> wrote: > > Hi everybody, > > > > I have a couple of questions regarding the performance requirements for a > > 12TB Riak cluster, specifically: > > Have you taken the default replication factor of 3 here, or is this > the sum of your data? > > > 1) I wonder if four servers, each one with the following spec, can handle > > it: 6 cores at 2.20GHz (15MB cache), 16GB of memory, and two 3TB HDD in a > > Raid 1 configuration. And if not, what would be the recommended number of > > machines we should provision. These machines are physical machines. We > > execute one or two M/R jobs per day, the scripts are written in Erlang. > > For production Riak deployments, we generally recommend a cluster with > 5 nodes or greater. [0] > > Beyond that, some decisions around backend, overall capacity, and > access patterns (anything outside of M/R) need to be taken into > consideration before validating a set of hardware specifications. A > high level guide of the decisions in the process are outlined here: > > - http://docs.basho.com/riak/latest/ops/building/planning/system-planning/ > - http://docs.basho.com/riak/latest/ops/building/planning/cluster/ > > > 2) Since we have two HDD per server in a Raid 1 configuration, I also > wonder > > if we can safely set the replication factor to one, since the data is > > already stored twice: if we lose an HDD, we still got the data on the > other > > one thanks to the Raid 1 conf. > > RAID 1 would cut your per node disk capacity in half (1.5TB), so at 4 > nodes, your overall cluster capacity would only be 6TB. > > For the N=1 question, I guess the best way to answer it is that Riak > maintains replicas within the system to facilitate high availability. > Any node or disk outage (or even scheduled maintenance) is going to > cause replicas to be unavailable in your cluster. This is generally > not desirable in any clustered configuration. > > > Thanks > > [0] > http://basho.com/why-your-riak-cluster-should-have-at-least-five-nodes/ > > > _______________________________________________ > > riak-users mailing list > > [email protected] > > http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com > > >
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