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From Josh Elser <josh.el...@gmail.com>
Subject Re: offload request to another tserver
Date Fri, 08 Jan 2016 23:05:23 GMT
z11373 wrote:
> I recall that I ever read somewhere that Accumulo is able to move tablets to
> other tservers if it experiences high load (i.e. read request) on one
> particular tserver, is that correct?

No, we don't rebalance tablet assignments on load. I believe the default 
balancer implementation tries to spread tablets for a specific table 
evenly across the available nodes. This is a pluggable implementation.

>  From the monitor page, one of the tservers that got heavy request would have
> at most 16 active scans, and often 3 digit number inside the parenthesis
> (i.e. # of scans waiting). I want to experiment if changing the max active
> scans would help the test run faster. Is it possible to change that max
> active scans number from 16 to a higher number?

Try increasing the following properties (I provided their defaults for you):

tserver.readahead.concurrent.max=16
tserver.scan.files.open.max=100

I remember writing up some really thorough documentation on how to use 
the configuration properties we have to really saturate your nodes, but 
I don't remember where that was. I'll try to find it :)

You can double check the Accumulo user manual on the website to see if 
we have some information there (that should be where we have the info).

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