You can get consistency by using Quorum, or write at All and read at one, or
write at one and read at All
Start with quorum.
If you read at one, then read repair will work in the background to fix the
data. But the result returned to your client may be inconsistent.
Aaron
On 12/02/2011, at 7:
What's the best practice in terms of consistency? I am assuming R+W > N
should be the best practice.
I thought even if R+W=N then there is some version level reconciliation that
kicks off if in case older version of the key/value is read. But to think of
it may not be possible. But then if R+W <=
eceived, it'll route it to one of them and not append anything to
its own commit log.
From: Ryan King [r...@twitter.com]
Sent: Friday, February 11, 2011 9:46 AM
To: user@cassandra.apache.org
Cc: cassandra-u...@incubator.apache.org
Subject: Re: Bas
On Fri, Feb 11, 2011 at 9:37 AM, mcasandra wrote:
>
> Is commit log file maintained on every node that's responsible to keep key
> ranges? So if Key A is supposed to go to Node, 1,2,3 then the commit log for
> Key A will be on each of these nodes? Is this commit log like redo log of
> oracle, whic
>I am trying to think why R + W > N is said to be consistent and not R + W =
N?
E.g RF of 4 - Write goes to nodes 1/2 and - in R+W=N case - Reads could
happen from 3/4. Does your write could be missed!
HTH,
-JA
On Fri, Feb 11, 2011 at 11:37 AM, mcasandra wrote:
>
> Is commit log file maintai
Is commit log file maintained on every node that's responsible to keep key
ranges? So if Key A is supposed to go to Node, 1,2,3 then the commit log for
Key A will be on each of these nodes? Is this commit log like redo log of
oracle, which is used in case of failure to roll forward/back the writes
"when a request comes in which node handles the request first"
You (ie. cassandra client) always specifies the exact node to send requests to.
While most higher level clients let's you specify configurations for a whole
cluster, that's usually for their own basic load balancing. Each request any
The client has to specify a node or a set of nodes in the cluster to connect
to. These nodes/this node will handle the request first.
In the cluster, nodes will gossip with each other about their information,
so that it will know which node has the key/value.
Stanley
On Fri, Feb 11, 2011 at 9:36
Take a look at the introduction here http://thelastpickle.com/2011/02/07/Introduction-to-Cassandra/ I've tried to cover the basic how the cluster works questions. Let me know if you have any suggestions on how I can improve it.Short answer is a Gossip protocol is used, every node knows about every
