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From J Mohamed Zahoor <jmo...@gmail.com>
Subject Re: consistency, availability and partition pattern of HBase
Date Wed, 08 Aug 2012 04:56:40 GMT
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 <wtan@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
> wtan@us.ibm.com; 914-784-6752
>
>
>
> From:   Lin Ma <linlma@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
>
>
>

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