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Date: Mon, 12 Nov 2012 18:12:05 -0800
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Subject: Re: Counter column families (pending replicate on write stage tasks)
From: Rob Coli <rcoli@palominodb.com>
To: user@cassandra.apache.org
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On Mon, Nov 12, 2012 at 3:35 PM, cem <cayiroglu@gmail.com> wrote:
> We are currently facing a performance issue with counter column families. I
> see lots of pending ReplicateOnWriteStage tasks in tpstats. Then I disabled
> replicate_on_write. It helped a lot. I want to use like that  but I am not
> sure how to use it.

Quoting Sylvain, one of the primary authors/maintainers of the
Counters support...

https://issues.apache.org/jira/browse/CASSANDRA-3868
"
I don't disagree about the efficiency of the valve, but at what price?
'Bootstrapping a node will make you lose increments (you don't know
which ones, you don't know how many and this even if nothing goes
wrong)' is a pretty bad drawback. That is pretty much why that option
makes me uncomfortable: it does give you better performance, so people
may be tempted to use it. Now if it was only a matter of replicating
writes only through read-repair/repair, then ok, it's pretty dangerous
but it's rather easy to explain/understand the drawback (if you don't
lose a disk, you don't lose increments, and you'd better use CL.ALL or
have read_repair_chance to 1). But the fact that it doesn't work with
bootstrap/move makes me wonder if having the option at all is not
making a disservice to users.
"

IOW, don't be tempted to turn off replicate_on_write. It breaks
counters. If you are under capacity at a steady state, increase
capacity.

=Rob

-- 
=Robert Coli
AIM&GTALK - rcoli@palominodb.com
YAHOO - rcoli.palominob
SKYPE - rcoli_palominodb