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From Dave Wang <...@cloudera.com>
Subject Re: Hbase Assignments in trunk.
Date Thu, 06 Sep 2012 14:36:07 GMT
There's a discussion on the ZK mailing list about releasing ZK 3.4.4, which
will have multi and some other fixes.  Once that is out, we can move to
that on trunk.  That will also help with one of the replication patches
that Himanshu currently has pending, which relies on multi.

- Dave

On Thu, Sep 6, 2012 at 3:20 AM, Jonathan Hsieh <jon@cloudera.com> wrote:

> IMO, moving to new ZK seems to  makes sense for HBase trunk.
>
> Jon.
>
> On Thu, Sep 6, 2012 at 12:53 AM, n keywal <nkeywal@gmail.com> wrote:
>
> > On the Async vs. sync: there are 3 different ways to write multiple
> znodes
> > in ZK, and huge differences in the performances between them:
> >
> > 1) for loop sync
> > 2) for loop async
> > 3) multi
> >
> > Async will be 20 to 100 times faster than sync. multi will be 2 to 4
> times
> > faster than async (that is, 80 to 400 times faster than sync).
> >
> > Multi was not available before ZK 3.4. It has several obvious advantages
> > over async imho: it's faster, it's synchronous and it's a transaction.
> That
> > simplifies the user code usually.
> >
> > It has other advantages:
> >  - async and sync will typically send 1 or more packet per znode (naggle
> is
> > not activated iirc), while there will be only a few packets for all the
> > znodes with multi
> >  - you can expect async to write multiple times on the disk, while multi
> > should write only once. This is usually better for i/o performances.
> >
> > On a serious recovery situation, with all the regions moving all other
> the
> > place, saving disk and network i/o for ZooKeeper is important.
> >
> > Disadvantage: it's new.
> >
> > On Thu, Sep 6, 2012 at 7:49 AM, Stack <stack@duboce.net> wrote:
> >
> > > On Wed, Sep 5, 2012 at 5:17 PM, Jonathan Hsieh <jon@cloudera.com>
> wrote:
> > > > Here's a link to the pdf/picture.
> > > >
> > > > http://people.apache.org/~jmhsieh/hbase/120905-hbase-assignment.pdf
> > > >
> > >
> > > Pretty picture.  Not a pretty story.
> > >
> > > What you thinking?
> > >
> > > St.Ack
> > >
> >
>
>
>
> --
> // Jonathan Hsieh (shay)
> // Software Engineer, Cloudera
> // jon@cloudera.com
>

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