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From Peter Schuller <peter.schul...@infidyne.com>
Subject Re: Consistency model
Date Mon, 18 Apr 2011 12:25:17 GMT
> Does anyone have any intuition about whether this will happen with
> consistency_level=ALL?  I will try it today, but I'd like to know what the
> expected behavior is.  It seems like it would not happen in this case.

Assuming my understanding is correct (see my comment in the JIRA
ticket), then I expect that you don't see the value reverting back to
an old version in your tests. However, this is not guaranteed. A read
on CL.ALL will see the most recent value as returned by *any* node.
However, suppose a failed write only is replicated to one node. That
node subsequently goes up in smoke and is replaced. Now you may revert
back to the old data unless the JIRA ticket is attended do.

But then, use of CL.ALL kind of implies that you're not willing to
accept downtime of any node. But it's important to keep in mind that
if you're looking for the kind of guarantee of not reverting to an
older value, then that "not loose a single node" applies not just to
being up and serving reads, but also to maintaining consistency over
time.

So while I expect that CL.ALL would not fail the test, I would not use
that information to conclude that the correct course of action is to
use CL.ALL ;)

-- 
/ Peter Schuller

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