incubator-cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Adi <adi.pan...@gmail.com>
Subject Re: atomicity
Date Sun, 19 Dec 2010 10:39:03 GMT
On Sat, Dec 18, 2010 at 11:02 PM, Kevin Irwig <kevinirwig@yahoo.com> wrote:

> Hi,
>
> Say I have two processes on separate machines, and a Cassandra cluster over
> several machines. If the first process writes (insert) to a column while
> the
> second process reads (get / get_slice / get_range_slices / others?) from
> that
> column (say the consistency level is QUORUM if that makes a difference), is
> the
> write "atomic", or could the second process get corrupt (half-written)
> data?
> What if Cassandra is not a cluster, but runs on a single machine? I'm
> currently
> using version 0.6.3, but the question is general.
>
>
The write is consistent if consistency level of write is QUORUM and read is
QUORUM
or according to the popular equation for strong consistency if R + W > N
where N = number of replicas, R = consistency level of read, W = consistency
level of write

On single machine with one node, consistency level of 1 for both R and W
will make the write consistent as again 1 + 1 > 1
Cassandra : The definitive guide - is a good resource for most questions
besides the wiki and mailing list.
http://oreilly.com/catalog/0636920010852

-Adi

Mime
View raw message