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From Chris Goffinet <goffi...@digg.com>
Subject Re: Read Performance
Date Wed, 31 Mar 2010 22:06:30 GMT
How many columns in each row?

-Chris

On Mar 31, 2010, at 2:54 PM, James Golick wrote:

> I just tried running the same multi_get against cassandra 1000 times, assuming that that'd
force it in to cache.
> 
> I'm definitely seeing a 5-10ms improvement, but it's still looking like 20-30ms on average.
Would you expect it to be faster than that?
> 
> - James
> 
> On Wed, Mar 31, 2010 at 11:44 AM, Jonathan Ellis <jbellis@gmail.com> wrote:
> But then you'd still be caching the same things memcached is, so
> unless you have a lot more ram you'll presumably miss the same rows
> too.
> 
> The only 2-layer approach that makes sense to me would be to have
> cassandra keys cache at 100% behind memcached for the actual rows,
> which will actually reduce the penalty for a memcache miss by
> half-ish.
> 
> On Wed, Mar 31, 2010 at 1:32 PM, David Strauss <david@fourkitchens.com> wrote:
> > Or, if faking memcached misses is too high a price to pay, queue some
> > proportion of the reads to replay asynchronously against Cassandra.
> >
> > On Wed, 2010-03-31 at 11:04 -0500, Jonathan Ellis wrote:
> >> Can you redirect some of the reads from memcache to cassandra?  Sounds
> >> like the cache isn't getting warmed up.
> >>
> >> On Wed, Mar 31, 2010 at 11:01 AM, James Golick <jamesgolick@gmail.com>
wrote:
> >> > I'm testing on the live cluster, but most of the production reads are being
> >> > served by the cache. It's definitely the right CF.
> >> >
> >> > On Wed, Mar 31, 2010 at 8:30 AM, Jonathan Ellis <jbellis@gmail.com>
wrote:
> >> >>
> >> >> On Wed, Mar 31, 2010 at 12:01 AM, James Golick <jamesgolick@gmail.com>
> >> >> wrote:
> >> >> > Okay, so now my row cache hit rate jumps between 1.0, 99.5, 95.6,
and
> >> >> > NaN.
> >> >> > Seems like that stat is a little broken.
> >> >>
> >> >> Sounds like you aren't getting enough requests for the
> >> >> getRecentHitRate to make sense.  use getHits / getRequests.
> >> >>
> >> >> But if you aren't getting enough requests for getRecentHitRate, are
> >> >> you sure you're tuning the cache on the right CF for your 35ms test?
> >> >> Are you testing live?  If not, what's your methodology here?
> >> >>
> >> >> -Jonathan
> >> >
> >> >
> >
> >
> >
> >
> 


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