Hi Pat, "thanks for that. Is the default on dw not also quorum though?? so, in my case it should be 2 (since I have 2 nodes)??"
Consider the difference in the usage of the word "node." There is actually a large difference between two definitions of the commonly used word, "node." 1. node: virtual node, as indicated by the ring_creation_size default value, which is 64, and can be changed in app.config. 2. node: physical node, which is the number of physical machines in a cluster. Historically and at the moment, virtual nodes are evenly divided amongst physical nodes. The term "node" has been conflated and continues to be a pain point for newcomers to Riak (not that you are a newcomer, but in general). In all cases, the values r, w, dw and considerations for quorum are entirely dependent on the replication value, known as n or n_val, which in turn represents replicas on a per virtual node basis. Hope that clears some stuff up, -Alexander Sicular @siculars On Sep 14, 2012, at 12:17 PM, Pat Lynch wrote: > Hi, > thanks for that. Is the default on dw not also quorum though?? so, in my > case it should be 2 (since I have 2 nodes)?? > > thanks, > Pat. > > Date: Fri, 14 Sep 2012 12:11:25 -0400 > Subject: Re: missing keys? > From: rzeze...@basho.com > To: plynch1...@hotmail.com > CC: s...@basho.com; riak-users@lists.basho.com > > Pat, > > On Fri, Sep 14, 2012 at 11:08 AM, Pat Lynch <plynch1...@hotmail.com> wrote: > > So, if I write a key to a cluster and then try to query that key, it may not > find it unless I retry? Even if r=2 & w=2 ? I thought that at least 2 > systems had to have that key (either in memory or disk) for the write to have > succeeded with those settings? If I had w=3, would you expect any missed > keys ?? (note that I didn't try that because I expected performance issues). > > It's important to note that `w` is considered complete once the value is > queued in-memory waiting to be written do disk [1]. A read does not check > the queue but only on-disk data. The `dw` flag is what you want to know that > the value has made it to disk and can be seen by a read. > > -Z > > [1]: https://github.com/basho/riak_kv/blob/master/src/riak_kv_vnode.erl#L284 > _______________________________________________ > riak-users mailing list > riak-users@lists.basho.com > http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com
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