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HBase >> mail # dev >> Hbase Assignments in trunk.


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Re: Hbase Assignments in trunk.
+1 on rethinking the assignment + splitting code paths, and using zk as a
transactional database. Just my 2 cents w/o spending a lot of time on the
details, but maybe we should stop keeping master and RS in memory metadata,
but keep region-assignments in zk, and HM and RS just keep a consistent
in-memory cache.

Enis

On Mon, Sep 10, 2012 at 3:29 PM, lars hofhansl <[EMAIL PROTECTED]> wrote:

> I've been saying a while ago that we should require ZK 3.4.x for 0.96+.
>
> Distributed consensus without a "transaction" option always rang a bit
> weird to me.
>
> Maybe switch in 0.98+?
>
> -- Lars
>
>
> ----- Original Message -----
> From: n keywal <[EMAIL PROTECTED]>
> To: [EMAIL PROTECTED]
> Cc:
> Sent: Thursday, September 6, 2012 12:53 AM
> Subject: Re: Hbase Assignments in trunk.
>
> 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 <[EMAIL PROTECTED]> wrote:
>
> > On Wed, Sep 5, 2012 at 5:17 PM, Jonathan Hsieh <[EMAIL PROTECTED]> 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
> >
>
>