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From Andrew Hulbert <>
Subject Re: Optimize Accumulo scan speed
Date Sun, 10 Apr 2016 15:25:03 GMT

Are you using a Scanner or a BatchScanner?

One thing we did in the past with a geohash-based schema was to prefix a 
shard ID in front of the geohash that allows you to involve all the 
tservers in the scan. You'd multiply your ranges by the number of 
tservers you have but if the client is not the bottleneck then it may 
increase your throughput.


On 04/10/2016 11:05 AM, Mario Pastorelli wrote:
> Hi,
> I'm currently having some scan speed issues with Accumulo and I would 
> like to understand why and how can I solve it. I have geographical 
> data and I use as primary key the day and then the geohex, which is a 
> linearisation of lat and lon. The reason for this key is that I always 
> query the data for one day but for a set of geohexes with represent a 
> zone, so with this schema I can scan use a single scan to read all the 
> data for one day with few seeks. My problem is that the scan is 
> painfully slow: for instance, to read 5617019 rows it takes around 17 
> seconds and the scan speed is 13MB/s, less than 750k scan entries/s 
> and around 300 seeks. I enable the tracer and this is what I've got
> 17325+0 Dice@srv1 Dice.query
> 11+1 Dice@srv1 scan 11+1 Dice@srv1 scan:location
> 5+13 Dice@srv1 scan 5+13 Dice@srv1 scan:location
> 4+19 Dice@srv1 scan 4+19 Dice@srv1 scan:location
> 5+23 Dice@srv1 scan 4+24 Dice@srv1 scan:location
> I'm not sure how to speedup the scanning. I have the following question:
>   - is this speed normal?
>   - can I involve more servers in the scan? Right now only two server 
> have the ranges but with a cluster of 15 machines it would be nice to 
> involve more of them. Is it possible?
> Thanks,
> Mario
> -- 
> Mario Pastorelli| TERALYTICS
> *software engineer*
> Teralytics AG | Zollstrasse 62 | 8005 Zurich | Switzerland
> phone:+41794381682
> email: 
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