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From Jing Zhao <ji...@apache.org>
Subject Re: Erasure coding in branch-2 [Was Re: [VOTE] Merge HDFS-7285 (erasure coding) branch to trunk]
Date Mon, 02 Nov 2015 21:22:15 GMT
Thanks for the discussion, Vinod and Andrew. Backporting EC to 2.9 sounds
good to me.

On Mon, Nov 2, 2015 at 12:06 PM, Andrew Wang <andrew.wang@cloudera.com>
wrote:

> Thanks for forking the thread Vinod,
>
> SGTM, though I really do recommend waiting for 2.9 given the current size
> of 2.8. I'm not a fan of an "off by default" half-measure, since it doesn't
> change our compatibility requirements, and there's some major NN surgery
> that can't really be disabled.
>
> If we do find a major user who's backported this to their own branch-2
> fork, I agree that's motivation to get it in an upstream release quicker. I
> haven't heard anything along these lines though.
>
> On Mon, Nov 2, 2015 at 11:49 AM, Vinod Vavilapalli <
> vinodkv@hortonworks.com>
> wrote:
>
> > Forking the thread. Started looking at the 2.8 list, various features’
> > status and arrived here.
> >
> > While I understand the pervasive nature of EC and a need for a
> significant
> > bake-in, moving this to a 3.x release is not a good idea. We will surely
> > get a 2.8 out this year and, as needed, I can even spend time getting
> > started on a 2.9. OTOH, 3.x is long ways off, and given all the
> > incompatibilities there, it would be a while before users can get their
> > hands on EC if it were to be only on 3.x. At best, this may force sites
> > that want EC to backport the entire EC feature to older releases, at
> worst
> > this will be repeat the mess of 0.20 security release forks.
> >
> > If we think adding this to 2.8 (even if it switched off) is too much risk
> > per our original plan, let’s move this to 2.9, there by leaving enough
> time
> > for stability, integration testing and bake-in, and a realistic chance of
> > having it end up on users’ clusters soonish.
> >
> > +Vinod
> >
> > > On Oct 19, 2015, at 1:44 PM, Andrew Wang <andrew.wang@cloudera.com>
> > wrote:
> > >
> > > I think our plan thus far has been to target this for 3.0. I'm okay
> with
> > > putting it in branch-2 if we've given a hard look at compatibility, but
> > > I'll note though that 2.8 is already looking like quite a large
> release,
> > > and our release bandwidth has been focused on the 2.6 and 2.7
> maintenance
> > > releases. Adding another multi-hundred JIRAs to 2.8 might make it too
> > > unwieldy to get out the door. If we bump EC past that, 3.0 might very
> > well
> > > be our next release vehicle. I do plan to revive the 3.0 schedule some
> > time
> > > next year. With EC and JDK8 in a good spot, the only big feature
> > remaining
> > > is classpath isolation.
> > >
> > > EC is also a pretty fundamental change to HDFS. Even if it's
> compatible,
> > in
> > > terms of size and impact it might best belong in a new major release.
> > >
> > > Best,
> > > Andrew
> > >
> > > On Fri, Oct 16, 2015 at 7:04 PM, Vinayakumar B <
> > > vinayakumarb.apache@gmail.com> wrote:
> > >
> > >> Is anyone else also thinks that feature is ready to goto branch-2  as
> > well?
> > >>
> > >> Its > 2 weeks EC landed on trunk. IMo Looks Its quite stable since
> then
> > and
> > >> ready to go in branch-2.
> > >>
> > >> -Vinay
> > >> On Oct 6, 2015 12:51 AM, "Zhe Zhang" <zhezhang@cloudera.com> wrote:
> > >>
> > >>> Thanks Vinay for capturing the issue and Uma for offering the help.
> > >>>
> > >>> ---
> > >>> Zhe Zhang
> > >>>
> > >>> On Mon, Oct 5, 2015 at 12:19 PM, Gangumalla, Uma <
> > >> uma.gangumalla@intel.com
> > >>>>
> > >>> wrote:
> > >>>
> > >>>> Vinay,
> > >>>>
> > >>>>
> > >>>> I would merge them as part of HDFS-9182.
> > >>>>
> > >>>> Thanks,
> > >>>> Uma
> > >>>>
> > >>>>
> > >>>>
> > >>>> On 10/5/15, 12:48 AM, "Vinayakumar B" <vinayakumarb@apache.org>
> > wrote:
> > >>>>
> > >>>>> Hi Andrew,
> > >>>>> I see CHANGES.txt entries not yet merged from
> > >> CHANGES-HDFS-EC-7285.txt.
> > >>>>>
> > >>>>> Was this intentional?
> > >>>>>
> > >>>>> Regards,
> > >>>>> Vinay
> > >>>>>
> > >>>>> On Wed, Sep 30, 2015 at 9:15 PM, Andrew Wang <
> > >> andrew.wang@cloudera.com>
> > >>>>> wrote:
> > >>>>>
> > >>>>>> Branch has been merged to trunk, thanks again to everyone
who
> worked
> > >>> on
> > >>>>>> the
> > >>>>>> feature!
> > >>>>>>
> > >>>>>> On Tue, Sep 29, 2015 at 10:44 PM, Zhe Zhang <
> zhezhang@cloudera.com>
> > >>>>>> wrote:
> > >>>>>>
> > >>>>>>> Thanks everyone who has participated in this discussion.
> > >>>>>>>
> > >>>>>>> With 7 +1's (5 binding and 2 non-binding), and no -1,
this vote
> > >> has
> > >>>>>> passed.
> > >>>>>>> I will do a final 'git merge' with trunk and work with
Andrew to
> > >>> merge
> > >>>>>> the
> > >>>>>>> branch to trunk. I'll update on this thread when the
merge is
> > >> done.
> > >>>>>>>
> > >>>>>>> ---
> > >>>>>>> Zhe Zhang
> > >>>>>>>
> > >>>>>>> On Thu, Sep 24, 2015 at 11:08 PM, Liu, Yi A <yi.a.liu@intel.com>
> > >>>>>> wrote:
> > >>>>>>>
> > >>>>>>>> (Change it to binding.)
> > >>>>>>>>
> > >>>>>>>> +1
> > >>>>>>>> I have been involved in the development and code
review on the
> > >>>>>> feature
> > >>>>>>>> branch. It's a great feature and I think it's ready
to merge it
> > >>> into
> > >>>>>>> trunk.
> > >>>>>>>>
> > >>>>>>>> Thanks all for the contribution.
> > >>>>>>>>
> > >>>>>>>> Regards,
> > >>>>>>>> Yi Liu
> > >>>>>>>>
> > >>>>>>>>
> > >>>>>>>> -----Original Message-----
> > >>>>>>>> From: Liu, Yi A
> > >>>>>>>> Sent: Friday, September 25, 2015 1:51 PM
> > >>>>>>>> To: hdfs-dev@hadoop.apache.org
> > >>>>>>>> Subject: RE: [VOTE] Merge HDFS-7285 (erasure coding)
branch to
> > >>> trunk
> > >>>>>>>>
> > >>>>>>>> +1 (non-binding)
> > >>>>>>>> I have been involved in the development and code
review on the
> > >>>>>> feature
> > >>>>>>>> branch. It's a great feature and I think it's ready
to merge it
> > >>> into
> > >>>>>>> trunk.
> > >>>>>>>>
> > >>>>>>>> Thanks all for the contribution.
> > >>>>>>>>
> > >>>>>>>> Regards,
> > >>>>>>>> Yi Liu
> > >>>>>>>>
> > >>>>>>>>
> > >>>>>>>> -----Original Message-----
> > >>>>>>>> From: Vinayakumar B [mailto:vinayakumarb@apache.org]
> > >>>>>>>> Sent: Friday, September 25, 2015 12:21 PM
> > >>>>>>>> To: hdfs-dev@hadoop.apache.org
> > >>>>>>>> Subject: Re: [VOTE] Merge HDFS-7285 (erasure coding)
branch to
> > >>> trunk
> > >>>>>>>>
> > >>>>>>>> +1,
> > >>>>>>>>
> > >>>>>>>> I've been involved starting from design and development
of
> > >>>>>> ErasureCoding.
> > >>>>>>>> I think phase 1 of this development is ready to
be merged to
> > >>> trunk.
> > >>>>>>>> It had come a long way to the current state with
significant
> > >>> effort
> > >>>>>> of
> > >>>>>>>> many Contributors and Reviewers for both design
and code.
> > >>>>>>>>
> > >>>>>>>> Thanks Everyone for the efforts.
> > >>>>>>>>
> > >>>>>>>> Regards,
> > >>>>>>>> Vinay
> > >>>>>>>>
> > >>>>>>>> On Wed, Sep 23, 2015 at 10:53 PM, Jing Zhao <jing9@apache.org>
> > >>>>>> wrote:
> > >>>>>>>>
> > >>>>>>>>> +1
> > >>>>>>>>>
> > >>>>>>>>> I've been involved in both development and
review on the
> > >> branch,
> > >>>>>> and
> > >>>>>> I
> > >>>>>>>>> believe it's now ready to get merged into trunk.
Many thanks
> > >> to
> > >>>>>> all
> > >>>>>>>>> the contributors and reviewers!
> > >>>>>>>>>
> > >>>>>>>>> Thanks,
> > >>>>>>>>> -Jing
> > >>>>>>>>>
> > >>>>>>>>> On Tue, Sep 22, 2015 at 6:17 PM, Zheng, Kai
<
> > >>> kai.zheng@intel.com>
> > >>>>>>> wrote:
> > >>>>>>>>>
> > >>>>>>>>>> Non-binding +1
> > >>>>>>>>>>
> > >>>>>>>>>> According to our extensive performance
tests, striping +
> > >> ISA-L
> > >>>>>> coder
> > >>>>>>>>> based
> > >>>>>>>>>> erasure coding not only can save storage,
but also can
> > >>> increase
> > >>>>>> the
> > >>>>>>>>>> throughput of a client or a cluster. It
will be a great
> > >>>>>> addition to
> > >>>>>>>>>> HDFS and its users. Based on the latest
branch codes, we
> > >> also
> > >>>>>>>>>> observed it's
> > >>>>>>>>> very
> > >>>>>>>>>> reliable in the concurrent tests. We'll
provide the perf
> > >> test
> > >>>>>> report
> > >>>>>>>>> after
> > >>>>>>>>>> it's sorted out and hope it helps.
> > >>>>>>>>>> Thanks!
> > >>>>>>>>>>
> > >>>>>>>>>> Regards,
> > >>>>>>>>>> Kai
> > >>>>>>>>>>
> > >>>>>>>>>> -----Original Message-----
> > >>>>>>>>>> From: Gangumalla, Uma [mailto:uma.gangumalla@intel.com]
> > >>>>>>>>>> Sent: Wednesday, September 23, 2015 8:50
AM
> > >>>>>>>>>> To: hdfs-dev@hadoop.apache.org;
> > >> common-dev@hadoop.apache.org
> > >>>>>>>>>> Subject: Re: [VOTE] Merge HDFS-7285 (erasure
coding) branch
> > >> to
> > >>>>>> trunk
> > >>>>>>>>>>
> > >>>>>>>>>> +1
> > >>>>>>>>>>
> > >>>>>>>>>> Great addition to HDFS. Thanks all contributors
for the nice
> > >>>>>> work.
> > >>>>>>>>>>
> > >>>>>>>>>> Regards,
> > >>>>>>>>>> Uma
> > >>>>>>>>>>
> > >>>>>>>>>> On 9/22/15, 3:40 PM, "Zhe Zhang" <zhezhang@cloudera.com>
> > >>> wrote:
> > >>>>>>>>>>
> > >>>>>>>>>>> Hi,
> > >>>>>>>>>>>
> > >>>>>>>>>>> I'd like to propose a vote to merge
the HDFS-7285 feature
> > >>>>>> branch
> > >>>>>>>>>>> back to trunk. Since November 2014
we have been designing
> > >> and
> > >>>>>>>>>>> developing this feature under the umbrella
JIRAs HDFS-7285
> > >>> and
> > >>>>>>>>>>> HADOOP-11264, and have committed approximately
210 patches.
> > >>>>>>>>>>>
> > >>>>>>>>>>> The HDFS-7285 feature branch was created
to support the
> > >> first
> > >>>>>> phase
> > >>>>>>>>>>> of HDFS erasure coding (HDFS-EC). The
objective of HDFS-EC
> > >> is
> > >>>>>> to
> > >>>>>>>>>>> significantly reduce storage space
usage in HDFS clusters.
> > >>>>>> Instead
> > >>>>>>>>>>> of always creating 3 replicas of each
block with 200%
> > >> storage
> > >>>>>> space
> > >>>>>>>>>>> overhead, HDFS-EC provides data durability
through parity
> > >>> data
> > >>>>>>> blocks.
> > >>>>>>>>>>> With most EC configurations, the storage
overhead is no
> > >> more
> > >>>>>> than
> > >>>>>>> 50%.
> > >>>>>>>>>>> Based on profiling results of production
clusters, we
> > >> decided
> > >>>>>> to
> > >>>>>>>>>>> support EC with the striped block layout
in the first
> > >> phase,
> > >>> so
> > >>>>>>>>>>> that small files can be better handled.
This means dividing
> > >>>>>> each
> > >>>>>>>>>>> logical HDFS file block into smaller
units (striping cells)
> > >>> and
> > >>>>>>>>>>> spreading them on a set of DataNodes
in round-robin
> > >> fashion.
> > >>>>>> Parity
> > >>>>>>>>>>> cells are generated for each stripe
of original data cells.
> > >>> We
> > >>>>>> have
> > >>>>>>>>>>> made changes to NameNode, client, and
DataNode to
> > >> generalize
> > >>>>>> the
> > >>>>>>>>>>> block concept and handle the mapping
between a logical file
> > >>>>>> block
> > >>>>>>>>>>> and its internal storage blocks. For
further details please
> > >>> see
> > >>>>>> the
> > >>>>>>>>>>> design doc on HDFS-7285.
> > >>>>>>>>>>> HADOOP-11264 focuses on providing flexible
and
> > >>> high-performance
> > >>>>>>>>>>> codec calculation support.
> > >>>>>>>>>>>
> > >>>>>>>>>>> The nightly Jenkins job of the branch
has reported several
> > >>>>>>>>>>> successful runs, and doesn't show new
flaky tests compared
> > >>> with
> > >>>>>>>>>>> trunk. We have posted several versions
of the test plan
> > >>>>>> including
> > >>>>>>>>>>> both unit testing and cluster testing,
and have executed
> > >> most
> > >>>>>> tests
> > >>>>>>>>>>> in the plan. The most basic functionalities
have been
> > >>>>>> extensively
> > >>>>>>>>>>> tested and verified in several real
clusters with different
> > >>>>>>>>>>> hardware configurations; results have
been very stable. We
> > >>> have
> > >>>>>>>>>>> created follow-on tasks for more advanced
error handling
> > >> and
> > >>>>>>>> optimization under the umbrella HDFS-8031.
> > >>>>>>>>>>> We also plan to implement or harden
the integration of EC
> > >>> with
> > >>>>>>>>>>> existing features such as WebHDFS,
snapshot, append,
> > >>> truncate,
> > >>>>>>>>>>> hflush, hsync, and so forth.
> > >>>>>>>>>>>
> > >>>>>>>>>>> Development of this feature has been
a collaboration across
> > >>>>>> many
> > >>>>>>>>>>> companies and institutions. I'd like
to thank J. Andreina,
> > >>>>>> Takanobu
> > >>>>>>>>>>> Asanuma, Vinayakumar B, Li Bo, Takuya
Fukudome, Uma
> > >> Maheswara
> > >>>>>> Rao
> > >>>>>>>>>>> G, Rui Li, Yi Liu, Colin McCabe, Xinwei
Qin, Rakesh R, Gao
> > >>> Rui,
> > >>>>>> Kai
> > >>>>>>>>>>> Sasaki, Walter Su, Tsz Wo Nicholas
Sze, Andrew Wang, Yong
> > >>>>>> Zhang,
> > >>>>>>>>>>> Jing Zhao, Hui Zheng and Kai Zheng
for their code
> > >>> contributions
> > >>>>>> and
> > >>>>>>>> reviews.
> > >>>>>>>>>>> Andrew and Kai Zheng also made fundamental
contributions to
> > >>> the
> > >>>>>>>>>>> initial design. Rui Li, Gao Rui, Kai
Sasaki, Kai Zheng and
> > >>> many
> > >>>>>>>>>>> other contributors have made great
efforts in system
> > >> testing.
> > >>>>>> Many
> > >>>>>>>>>>> thanks go to Weihua Jiang for proposing
the JIRA, and ATM,
> > >>> Todd
> > >>>>>>>>>>> Lipcon, Silvius Rus, Suresh, as well
as many others for
> > >>>>>> providing
> > >>>>>>>> helpful feedbacks.
> > >>>>>>>>>>>
> > >>>>>>>>>>> Following the community convention,
this vote will last
> > >> for 7
> > >>>>>> days
> > >>>>>>>>>>> (ending September 29th). Votes from
Hadoop committers are
> > >>>>>> binding
> > >>>>>>>>>>> but non-binding votes are very welcome
as well. And here's
> > >> my
> > >>>>>>>>>>> non-binding
> > >>>>>>>>> +1.
> > >>>>>>>>>>>
> > >>>>>>>>>>> Thanks,
> > >>>>>>>>>>> ---
> > >>>>>>>>>>> Zhe Zhang
> > >>>>>>>>>>
> > >>>>>>>>>>
> > >>>>>>>>>
> > >>>>>>>>
> > >>>>>>>
> > >>>>>>
> > >>>>
> > >>>>
> > >>>
> > >>
> >
> >
>

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