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From Azuryy Yu <azury...@gmail.com>
Subject Re: what's the typical scan latency?
Date Mon, 03 Jun 2013 09:21:38 GMT
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.vasudevan@gmail.com> wrote:

> What is that you are observing now?
>
> Regards
> Ram
>
>
> On Mon, Jun 3, 2013 at 2:00 PM, Liu, Raymond <raymond.liu@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
> >
>

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