It would certainly depend on the nuances of your definitions! Especially
since you added this monster of a caveat: " in the absence of failures".
Here's a scenario for you: 1) Write at quorum, 2) Add 3 nodes, 3)
Immediately read at [the new] quorum - no guarantee that the new nodes will
have fully bootstrapped.
Who knows how many other modalities there might be - despite however many
caveats you want to tack on.
"Strong consistency" is a "model", not necessarily a reality at any point in
time even if it was a reality at a prior point in time.
If I deliberately "decommission" a node, that isn't necessarily a "failure"
is it?
All of that said, "it depends" on where you're trying to get to.
-- Jack Krupansky
-----Original Message-----
From: William Katsak
Sent: Wednesday, October 8, 2014 7:19 PM
To: user@cassandra.apache.org
Subject: Re: Consistency Levels
Thanks.
I am thinking more in terms of the combination of read/write. If I am
correct, QUORUM reads and QUORUM writes (or ONE-ALL) should deliver
strong consistency in the absence of failures, correct? Or this this
still considered eventual consistency, somehow?
-Bill
On 10/08/2014 06:17 PM, Jack Krupansky wrote:
I don't know of any such data collected by DataStax - it's not like
we're the NSA, sniffing all requests.
ONE is certainly fast, but only fine if you don't have immediate need to
read the data or don't need the absolutely most recent value.
To be clear, even QUORUM write is eventual consistency - to all nodes
beyond the immediate quorum.
-- Jack Krupansky
-----Original Message----- From: William Katsak
Sent: Wednesday, October 8, 2014 12:27 PM
To: user@cassandra.apache.org
Subject: Consistency Levels
Hello,
I was wondering if anyone (Datastax?) has any usage data about
consistency levels. For example, what consistency levels are real
applications using in real production scenarios. Who is using eventual
consistency (ONE-ONE) in production vs strong consistency
(QUORUM-QUORUM, ONE-ALL). Obviously it depends on the application, but I
am trying to collect some information on this.
I saw the talk from Christos Kalantzis (from Cassandra13 I think) about
Netflix using eventual consistency, but I was wondering if there is any
more data out there.
Thanks in advance,
Bill Katask
Ph.D. Student
Department of Computer Science
Rutgers University
--
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William Katsak <wkat...@cs.rutgers.edu>
Ph.D. Student
Rutgers University
Department of Computer Science
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