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From chovatia jaydeep <chovatia_jayd...@yahoo.co.in>
Subject Re: Will writes with < ALL consistency eventually propagate?
Date Mon, 07 Nov 2011 06:14:10 GMT
Hi Riyad,

You can set replication = 5 (number of replicas) and write with CL = ONE. There is no hard
requirement from Cassandra to write with CL=ALL to replicate the data unless you need it.
Considering your example, If you write with CL=ONE then also it will replicate your data to
all 5 replicas eventually.

Thank you,

Jaydeep

________________________________
From: Riyad Kalla <rkalla@gmail.com>
To: "user@cassandra.apache.org" <user@cassandra.apache.org>
Sent: Sunday, 6 November 2011 9:50 PM
Subject: Will writes with < ALL consistency eventually propagate?

I am new to Cassandra and was curious about the following scenario...

Lets say i have a ring of 5 servers. Ultimately I would like each server to be a full replication
of the next (master-master-*). 

In a presentation i watched today on Cassandra, the presenter mentioned that the ring members
will shard data and route your requests to the right host when they come in to a server that
doesnt physically contain the value you wanted. To the client requesting this is seamless
excwpt for the added latency.

If i wanted to avoid the routing and latency and ensure every server had the full data set,
do i have to write with a consistency level of ALL and wait for all of those writes to return
in my code, or can i write with a CL of 1 or 2 and let the ring propagate the rest of the
copies to the other servers in the background after my code has continued executing?

I dont mind eventual consistency in my case, but i do (eventually) want all nodes to have
all values and cannot tell if this is default behavior, or if sharding is the default and
i can only force duplicates onto the other servers explicitly with a CL of ALL.

Best,
Riyad
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