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From Josh Elser <josh.el...@gmail.com>
Subject Re: question on data block cache
Date Fri, 22 Jan 2016 19:35:41 GMT
A Tablet is hosted by one and only one TabletServer at any time. The 
only data you are querying is in Tablet(s) hosted by that one TabletServer.

Add more splits to the table which you are heavily querying to spread 
the load across many TabletServers. Load is parallelized in Accumulo by 
creating multiple Tablets (via splits) which can be spread across 
multiple servers.

z11373 wrote:
> Another observation which I really want to know why.
>
> I see 1 tablet server consistently shows high number of waiting scans, i.e.
> '16 (435)' or '14 (476)' on Running Scans column, while the other 19 tablet
> servers all showing '0 (0)' or sometimes showing single digit number. The
> thing I don't understand is what I've seen from the Monitor UI for a table
> at one snapshot for example, and this is more or less consistent from time
> to time (when the test clients are still running).
>
> Server | Query | Running Scans
> ====================
> TServer1 | 24 | 0 (0)
> TServer2 | 37 | 0 (0)
> TServer3 | 40 | 0 (0)
> TServer4 | 1 | 0 (0)
> TServer5 | 0 | 0 (0)
> TServer6 | 57 | 0 (0)
> TServer7 | 5 | 0 (0)
> TServer8 | 4 | 0 (0)
> TServer9 | 7 | 0 (0)
> TServer10 | 0 | 0 (0)
> TServer11 | 56 | 0 (0)
> TServer12 | 124 | 0 (0)
> TServer13 | 25 | 0 (0)
> TServer14 | 121 | 16 (435)
> TServer15 | 36 | 0 (0)
> TServer16 | 21 | 0 (0)
> TServer17 | 3 | 0 (0)
> TServer18 | 107 | 0 (0)
> TServer19 | 21 | 0 (0)
> TServer20 | 92 | 0 (0)
>
> I'd really appreciate if someone could explain what may have happened, or
> can point me to the right direction for starting the investigation. For the
> record, there are 50 test clients, each may create multiple scanners to
> query different data from that table.
>
> Thanks,
> Z
>
>
>
> --
> View this message in context: http://apache-accumulo.1065345.n5.nabble.com/question-on-data-block-cache-tp15906p15934.html
> Sent from the Developers mailing list archive at Nabble.com.

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