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From A J <s5a...@gmail.com>
Subject Re: Understand eventually consistent
Date Fri, 18 Feb 2011 18:26:07 GMT
#1, R=2, so if only one machine is up, by definition R cannot be
satisfied. So it will not return.

#2, consistency is an involved topic with no quick and easy
explanation and answers. my 2 cents,
Question of eventual consistency comes in distributed systems, where
you can write to one machine but read from another machine.

If it is not distributed and just one machine, then ofcourse you will
always read your write and be strongly consistent.
Check the post:
http://www.allthingsdistributed.com/2007/12/eventually_consistent.html

Also cassandra is not really eventually consistent but tunable
consistency. You can make it strongly consistent at the cost of
availability.  Check the video and slides out at:
http://cassandra.apache.org/


On Fri, Feb 18, 2011 at 12:53 PM, mcasandra <mohitanchlia@gmail.com> wrote:
>
> I have couple of more quesitons:
>
> 1. What happens when RF = 3, R = 2 and W = 2 and 2 machines go down? Would
> read and write fail or get the results from that one machine that is up?
> 2. Someone in this thread mentioned that write is eventually consistent. Is
> it because response is returned to the client as soon as data is written to
> commit log. But isn't this same as other RDBMS? Oracle does the same thing
> it writes to REDO log and somepoint later does a checkpoint and flushes data
> to disk. But RDBMS is not called eventually consistent.
> --
> View this message in context: http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/Understand-eventually-consistent-tp6038330p6040893.html
> Sent from the cassandra-user@incubator.apache.org mailing list archive at Nabble.com.
>

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