Depends on so much environment related variables and on data as well. But to give you a number after all: One of our clusters is on EC2, 6 RS, on m1.xlarge machines (network performance 'high' according to aws), with 90% of the time we do reads; our avg data size is 2K, block cache at 20K, 100 rows per scan avg, bloom filters 'on' at the 'ROW' level, 40% of heap dedicated to block cache (note that it contains several other bits and pieces) and I would say our average latency for cached data (~97% blockCacheHitCachingRatio) is 3-4ms. File system access is much much painful, especially on ec2 m1.xlarge where you really can't tell what's going on, as far as I can tell. To tell you the truth as I see it, this is an abuse (for our use case) of the HBase store and for cache like behavior I would recommend going to something like Redis.
On Mon, Jun 3, 2013 at 12:13 PM, ramkrishna vasudevan < ramkrishna.s.vasude...@gmail.com> wrote: > What is that you are observing now? > > Regards > Ram > > > On Mon, Jun 3, 2013 at 2:00 PM, Liu, Raymond <raymond....@intel.com> > wrote: > > > Hi > > > > If all the data is already in RS blockcache. > > Then what's the typical scan latency for scan a few rows from a > > say several GB table ( with dozens of regions ) on a small cluster with > say > > 4 RS ? > > > > A few ms? Tens of ms? Or more? > > > > Best Regards, > > Raymond Liu > > >
