Hi Lin, I would suggest reading this for more clarity.
http://www.cloudera.com/blog/2010/04/cap-confusion-problems-with-partition-tolerance/ ./zahoor On Wed, Aug 8, 2012 at 9:48 AM, Wei Tan <w...@us.ibm.com> wrote: > Hi Lin, > > In the CAP theorem > Consistency stands for atomic consistency, i.e., each CRUD operation > occurs sequentially in a global, real-time clock > Availability means each server if not partitioned can accept requests > > Partition means network partition > > As far as I understand (although I do not see any official documentation), > HBase achieved "per key sequential consistency", i.e., for a specific key, > there is an agreed sequence, for all operations on it. This is weaker than > strong or sequential consistency, but stronger than "eventual > consistency". > > BTW: CAP was proposed by Prof. Eric Brewer... > http://en.wikipedia.org/wiki/Eric_Brewer_%28scientist%29 > > Best Regards, > Wei > > Wei Tan > Research Staff Member > IBM T. J. Watson Research Center > 19 Skyline Dr, Hawthorne, NY 10532 > w...@us.ibm.com; 914-784-6752 > > > > From: Lin Ma <lin...@gmail.com> > To: user@hbase.apache.org, > Date: 08/07/2012 09:30 PM > Subject: consistency, availability and partition pattern of HBase > > > > Hello guys, > > According to the notes by Werner*, "*He presented the CAP theorem, which > states that of three properties of shared-data systems—data consistency, > system availability, and tolerance to network partition—only two can be > achieved at any given time." => > http://www.allthingsdistributed.com/2008/12/eventually_consistent.html > > But it seems HBase could achieve all of the 3 features at the same time. > Does it mean HBase breaks the rule by Werner. :-) > > If not, which one is sacrificed -- consistency (by using HDFS), > availability (by using Zookeeper) or partition (by using region / column > family) ? And why? > > regards, > Lin > > >
