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From Jean-Daniel Cryans <jdcry...@apache.org>
Subject Early comparisons between 0.90 and 0.92
Date Thu, 15 Dec 2011 01:26:38 GMT
Hey guys,

I was doing some comparisons between 0.90.5 and 0.92.0, mainly
regarding reads. The numbers are kinda irrelevant but the differences
are. BTW this is on CDH3u3 with random reads.

In 0.90.0, scanning 50M rows that are in the OS cache I go up to about
1.7M rows scanned per second.

In 0.92.0, scanning those same rows (meaning that I didn't run
compactions after migrating so it's picking the same data from the OS
cache), I scan about 1.1 rows per second.

0.92 is 50% slower when scanning.

In 0.90.0 random reading 50M rows that are OS cached I can do about
200k reads per second.

In 0.92.0, again with those same rows, I can go up to 260k per second.

0.92 is 30% faster when random reading.

I've been playing with that data set for a while and the numbers in
0.92.0 when using HFileV1 or V2 are pretty much the same meaning that
something else changed or the code that's generic to both did.

I'd like to be able to associate those differences to code changes in
order to understand what's going on. I would really appreciate if
others also took some time to test it out or to think about what could
cause this.



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