On Apr 10, 2013, at 2:26 PM, Tom Zeng <[email protected]> wrote:
> Hi list, > > We have a production installation with only 3 nodes and running on 1.2.1. > I'd appreciate to get some facts to convince IT to increase the number of > nodes to 7 and upgrade to 1.3. I heard people from Basho mentioned ideally 7 > nodes for production a couple of time, can someone explain why 7, is 4, or 5 > nodes good enough? I'm not sure where you heard the number 7 as a minimum, unless if was for a specific use-case. In general the minimum recommended number is 5 nodes. Running with only 3 nodes isn't a great idea. Since a core purpose of Riak is to remain available in the face of outages, 3 will not support any outage. Less than 3 is lower than the default replication value (N=3). This is so important, in fact, that we recommend 5 solely to act as a buffer in the case where 1 of the 5 is down, the remaining 4 is dangerously close to the inflexible 3 node number. Even if you do not upgrade to 1.3, you really need to have at least 5 nodes. There are many benefits to upgrading to 1.3, but one of the most compelling from an operations point of view is active anti-entropy (AAE). Rather than waiting on read-repair to fix inconsistent values (which is passive), AAE routinely attempts to keep all node values in sync. This can be a godsend if a node goes down, since you don't need to fore read-repair when you bring the node back up by reading every key... you just let your cluster actively self-heal. > Also on the 3 three nodes, the file size for the bitcask directory very quite > a bit: 21GB, 14GB, and 20GB. Could the node with only 14GB missing something > or it's expected to have such big difference? There are several reasons sizes could be different. Values are not yet/ever replicated (based on your N and W values). Files may have not been compacted. Some keys have been deleted but not yet reaped... > Thanks, > Tom > > -- > Tom Zeng > Director of Engineering > Intridea, Inc. | www.intridea.com > [email protected] > (o) 888.968.4332 x519 > (c) 240-643-8728 > _______________________________________________ > riak-users mailing list > [email protected] > http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com
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