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From Andrew Purtell <apurt...@apache.org>
Subject Re: Cassandra vs HBase
Date Tue, 01 Sep 2009 20:51:53 GMT
>From my point of view the biggest difference between the two systems is the following:
Cassandra can always accept writes. It uses its own local storage (no dependence on HDFS or
anything like that) and P2P data replication. In contrast, HBase depends on HDFS so is unavailable
if the filesystem has a problem, and furthermore if regions are in transition due to node
failure or load balancing then writes to the affected region are temporarily blocked until
it is available again. In exchange for always accepting writes, depending on what fails where
and when, reads in Cassandra may only retrieve stale data, or the reads of some clients can
be inconsistent with reads of others. Eventually all reads will return the last written value.
In contrast, HBase and Hypertable and Google's implementation are strongly consistent systems.
A read always returns the last written value. 

In the proposed HBase replication system (HBASE-1295), each peer cluster is strongly consistent
but edits will be asynchronously propagated between them -- we call this regional consistency.


    - Andy



On Tue, Sep 1, 2009 at 11:45 AM, charles du <taiping.du@gmail.com> wrote:

> Hi:
>
> Does anyone have experience with both Cassandra and HBase? To me, they
> target at a similar problem. I am wondering what are main differences
> between these two, like reliablity/performance/features?
>
> Thanks.
>
> --
> tp
>



      
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