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From Jonathan Hsieh <...@cloudera.com>
Subject Re: Hbase Assignments in trunk.
Date Thu, 06 Sep 2012 10:20:41 GMT
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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