Oh, I thought the rule was "if you have one more node than your n_val, then you can be sure each replica will be on a distinct node" - is that not correct?
Also with n of 2 I would wonder how you would handle r and w - my guess would be you *could* set them to 1 each, and just deal with possible consistency issues if you lost a node. But it would be 'weird' in that you wouldn't really have a quorum to make - it'd be "whoever is up right now wins". And then - when the downed node comes back - you might spit back inconsistent answers until AAE fixes up your data. Read-repair would *not* end up fixing your data up, because the r value of 1 would be satisfied. Does that sound right? I'm asking not only for the original poster; but to make sure I understand what I've got here for myself too! -B. On Thu, Aug 22, 2013 at 1:41 PM, Kelly McLaughlin <ke...@basho.com> wrote: > Idan, > > Actually in the case you described of using a 3 node Riak cluster with > n_val of 2 the behavior you see makes perfect sense. When using only three > nodes Riak does not guarantee that all replicas of an object will be on > distinct physical nodes. So if you have one node down you can hit a case > where both of the replicas of an object stored in Riak live on the downed > node. This explains the reason you see occasional failure to retrieve an > object with s3cmd, but most of the time it works just fine. It is for this > reason we strongly recommend people to use at least 5 nodes in their > production deployments. For testing, using at least use 4 nodes in the > cluster will likely reduce the chances of this situation occurring versus > using only 3. > > Also just be very cautious about reducing the n_val to 2. You will save on > storage space doing that, but there is a trade-off to be made in > availability and performance in doing so. > > Hope that helps shed some light. > > Kelly > > On August 22, 2013 at 10:12:06 AM, Idan Shinberg (idan.shinb...@idomoo.com) > wrote: > > Thanks for the aid > > This is a testing environemt . no-one accesses it aside of me > > Prior to creating the objects via riak-cs , I set the cluster to n_val 2 > for the default bucket props . > On that empty cluster , i started creating objects . ( around 500) . > Then I stopped and killed one of the nodes . > Then the issues mentioned above were seen. > > still doesn't make any sense... > > Regards, > > Idan Shinberg > > > System Architect > > Idomoo Ltd. > > > > Mob +972.54.562.2072 > > email idan.shinb...@idomoo.com > > web www.idomoo.com > > [image: Description: > file:///Users/kelly/Library/Containers/it.bloop.airmail/Data/Library/Application > Support/Airmail/General/Local/1377192732334581760/Attachments/fc66336e-e750-4c2d-b6e3-985d5a06b...@idomoo.co.il] > > > _______________________________________________ > riak-users mailing list > riak-users@lists.basho.com > http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com > >
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