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From Konstantin Shvachko <shv.had...@gmail.com>
Subject Re: Update on hadoop-0.23
Date Sun, 02 Oct 2011 02:13:59 GMT
I am very glad that the development and testing of 0.23 is going so well.
I see a lot of commits and hundreds of changes going in literally every day.
It is great to see the new technology building!

On the criticism of the 0.22 release.
Arun has a top-down view and I agree a lot of progress have been
achieved with the framework.
My bottom-up view is that you first need a reliable storage layer. If
the file system looses blocks or worse messes up with the image and/or
journals, the performance of the framework is your second problem. I
have said that before. Based on my experience it take time to
stabilize a file system. Anybody seen one that has been stabilized in
less than 2 years?
I do not see the 0.22 release as a wasted effort. And if the progress
with it contributes to the 0.23 rush I am twice as happy.


On Fri, Sep 30, 2011 at 3:00 PM, Arun C Murthy <acm@hortonworks.com> wrote:
> On Sep 30, 2011, at 1:13 PM, Todd Lipcon wrote:
>> On Fri, Sep 30, 2011 at 11:44 AM, Roman Shaposhnik <rvs@apache.org> wrote:
>>> I apologize if my level of institutional knowledge of these things is
>>> lacking, but do you have any
>>> benchmarking results between 0.22 and 0.20.2xx? The reason I'm asking
>>> is twofold -- I really
>>> would like to see an objective numbers qualifying the viability of
>>> 0.22 from the performance stand point,
>>> but more importantly I would really like to include the benchmarking
>>> code into Bigtop.
>> 0.22 currently suffers from MAPREDUCE-2266, which, last time I
>> benchmarked it, caused a significant slowdown. iirc a terasort ran
>> something like twice as slow on my test cluster due to this bug.
>> 0.23/MR2 doesn't suffer from this bug.
> I don't really know where to start. CHANGES.txt in branch-0.20-security has the full
> If I remember right, long ago (late 2009)  we benchmarked .21 with gridmix and saw >30%
prior to abandoning .21.
> Since then 0.20.2xx has had innumerable improvements to JobTracker, TaskTracker etc.
> # JobTracker itself is almost thrice as fast as it used to be in 2009.
> # The scheduler is significantly better (>2x locality) and throughput.
> # TaskTracker has had innumerable fixes for dist.cache, task launch, shutdown (MR-2266
and lots of other similar fixes).
> # The MR runtime has fixes for latency on innumerable fronts.
> Other regressions:
> # Security
> # Support for multi-tenant clusters.
> # Tonnes of operability fixes (jobhistory, task logs i.e. MR-1100) for running MR clusters.
> The one redeeming aspect for .22 is the shuffle based on the work we did for winning
Terasort/Petasort in 2009 but 0.23 has even more work there with zero-copy with netty (yaay!
no more jetty! Thanks to @cdouglas).
>> In terms of bugs -- same question. Is there any publicly available
>> list of, at least, the critical
>> ones that make 0.22 not viable from your point of view?
> We marked a lot of them as blockers on .22 and they were discarded by the release master(s).
branch-0.20-security/CHANGES.txt is the full list. I really can't spend time enumerating over
4000 commits and > 2000 (?) jiras to that branch at this point.
> In my opinion, as someone who has helped develop/run/support very large installs and
done this for over 5 1/2 years, a major release with regression on features (security, multi-tenancy)
and scalability, performance etc. is distinctly _unviable_.
> ----
> Again, none of this is meant to say you should invest time on fixing them or releasing
0.22 as it stands - just, please, don't label it in a manner which helps build unreasonable
expectations among users about it's viability & usability.
> thanks,
> Arun

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