What does the CFS mbean think read latencies are? Possibly something else is introducing latency after the read.
On Wed, Mar 31, 2010 at 5:37 PM, James Golick <jamesgol...@gmail.com> wrote: > Standard CF. 10 columns per row. Between about 800 bytes and 2k total per > row. > On Wed, Mar 31, 2010 at 3:06 PM, Chris Goffinet <goffi...@digg.com> wrote: >> >> 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 <jbel...@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 <da...@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 <jamesgol...@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 <jbel...@gmail.com> >>> >> > wrote: >>> >> >> >>> >> >> On Wed, Mar 31, 2010 at 12:01 AM, James Golick >>> >> >> <jamesgol...@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 >>> >> > >>> >> > >>> > >>> > >>> > >>> > >> >> > >
