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Accumulo, mail # dev - ingest performance oscillations and Xceivers


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Re: ingest performance oscillations and Xceivers
John Vines 2013-01-03, 23:04
How many hard drives and what's your max minor/maor compactions set to?
These can severely limit your performance due to potential disk thrashing.
If you observe the monitor, when ingest starts trailing, do you see it
undergoing, or possibly being backed up on, any form of compaction? And
lastly, are you see the bug eric mentioned above? See if the monitor is
reporting any warnings like those mentioned.
On Thu, Jan 3, 2013 at 5:25 PM, Jeremy Kepner <[EMAIL PROTECTED]> wrote:

> No correlation with compactions.  No queries.
>
> On Thu, Jan 03, 2013 at 11:24:17AM -0500, William Slacum wrote:
> > Have you also been tracking compactions? Did you have a query load?
> >
> >
> > On Wed, Jan 2, 2013 at 7:25 PM, Kepner, Jeremy - 0553 - MITLL <
> > [EMAIL PROTECTED]> wrote:
> >
> > > Hmmm, that's interesting, because in the past I didn't see this
> behavior.
> > >  It might be worth having someone look into because it seems to have a
> 2x
> > > impact on sustained ingest.
> > >
> > > Regards.  -Jeremy
> > >
> > > On Jan 2, 2013, at 2:23 PM, Keith Turner wrote:
> > >
> > > > On Wed, Jan 2, 2013 at 2:11 PM, Jeremy Kepner <[EMAIL PROTECTED]>
> wrote:
> > > >> So what mechanism causes the number of Xceivers to increase?
> > > >
> > > > Its been a while since I looked at the data node source code.   When
> I
> > > > last look at it an Xceiver was just a thread created to handle a
> > > > datanode request.   The thread went away after the request was
> > > > processed.   So major and minor compactions running would cause more
> > > > Xceivers to be created to read and write data.
> > > >
> > > > Newer datanode code may use a thread pool instead of creating a
> > > > thread/xceiver for each request.   I am not sure.
> > > >
> > > >> I am carefully controlling the number of ingestors and the data
> isn't
> > > varying too much.
> > > >> I would expect the number of Xceivers to remain consant.
> > > >>
> > > >> Regards.  -Jeremy
> > > >>
> > > >> On Tue, Jan 01, 2013 at 09:45:20PM -0500, Eric Newton wrote:
> > > >>> Hey Jeremy,
> > > >>>
> > > >>> Can you compare the ingest rate to the number of tablets, too?
> > > >>>
> > > >>> I've found, that if I have 20-80 tablets per server (on similar
> > > hardware) I
> > > >>> get the best performance.
> > > >>>
> > > >>> # of Xceivers == number of writers when ingest is the primary
> target.
> > > >>>
> > > >>> Also, is this 1.4 or trunk?
> > > >>>
> > > >>> -Eric
> > > >>>
> > > >>>
> > > >>>
> > > >>> On Tue, Jan 1, 2013 at 9:19 PM, Kepner, Jeremy - 1010 - MITLL <
> > > >>> [EMAIL PROTECTED]> wrote:
> > > >>>
> > > >>>> Accumulo Colleagues,
> > > >>>>  I am trying to optimize my ingest into a single node Accumulo
> > > instance
> > > >>>> running on a 32 core node with 96 GB of RAM.  I am seeing the
> follow
> > > ingest
> > > >>>> variations as a I change the number of ingest processes (see
> > > attached):
> > > >>>>
> > > >>>> -------------------------------------
> > > >>>> Ingestors, Ingest rate
> > > >>>> -------------------------------------
> > > >>>> 1, 60K inserts/sec (stable)
> > > >>>> 2, 120K inserts/sec (stable)
> > > >>>> 3, 60K to 180K inserts/sec
> > > >>>> 4, 90K to 220K inserts/sec
> > > >>>> 8, 80K to 280K inserts/sec
> > > >>>> 12, 80K to 280K inserts/sec
> > > >>>> -------------------------------------
> > > >>>>
> > > >>>> The only thing I can see that correlates with the ingest rate is
> the
> > > >>>> number of Xceivers.  When the ingest rate is high the number of
> > > Xceivers is
> > > >>>> usually low.  Likewise, when the ingest rate drops, the number of
> > > Xceivers
> > > >>>> usually increases significantly.
> > > >>>>
> > > >>>> Question: What role to Xceivers play in ingest?
> > > >>>>
> > > >>>> Request: It would be great to add a plot showing the number of
> > > Xceivers
> > > >>>> over time to the diagnostics.
> > > >>>>
> > > >>>> Regards.  -Jeremy
> > > >>>>
> > > >>>>
> > >
> > >
>