Thanks Eric for the info, that's very helpful. 7 was mentioned at the last Riak DC meetup. not as the minimal but for better performance, when I was chatting with a couple of Basho devs about performance benchmarking, and about Riak is quite a bit slower on single node against Mongo.
On Wed, Apr 10, 2013 at 5:56 PM, Eric Redmond <[email protected]> wrote: > > > 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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