HBase doesn't know all data are in the block cache. it had to look at HTable firstly to get "block_id"(tablename + offset), then find it in the block cache.
so if all data in the block cache, you just avoid to read data from hfile directly, save some I/O time. but it depends on your data size. if you always return a large data size, the read performance cannot be improved. On Mon, Jun 3, 2013 at 5:13 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 > > >
