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From Hari Sreekumar <hsreeku...@clickable.com>
Subject Re: Zookeeper quorum config
Date Thu, 09 Dec 2010 09:49:24 GMT
I have master also serving as regionserver. I'll run ZK also on 3 of the
regionservers. I don't have too much data (few TBs only), so I guess it
would be fine?


On Thu, Dec 9, 2010 at 12:44 AM, Ted Dunning <tdunning@maprtech.com> wrote:

> Ahh... that is very much at the other end of the spectrum from what I am
> used to.
>
> Yes.  It would not be good to run ZK on a system where the disk is
> essentially unavailable for
> significant amounts of time.
>
> On Wed, Dec 8, 2010 at 10:24 AM, Jean-Daniel Cryans <jdcryans@apache.org
> >wrote:
>
> > Ted,
> >
> > Sorry, wrong choice of words, HBase will be unreliable. I'm referring
> > to a situation where the session timeout is caused by a very slow
> > quorum because, as I saw it happening before, the datanodes where
> > pegging the disk(s) while being hammered by the region servers.
> >
> > J-D
> >
> > On Wed, Dec 8, 2010 at 10:20 AM, Ted Dunning <tdunning@maprtech.com>
> > wrote:
> > > This is a bit misleading.  ZK is always reliable regardless of disk
> > latency.
> > >  All that happens on a busy disk is that
> > > you get longer latency for ZK transactions.  For a dedicated and
> > > well-configured machine, you can have average
> > > latency (including committing to disk) of about 7 ms.  For a
> > multi-purpose
> > > busy machine, you may see latencies
> > > of 300 ms.
> > >
> > > Neither case will cause unreliable operation.
> > >
> > > On Wed, Dec 8, 2010 at 10:14 AM, Jean-Daniel Cryans <
> jdcryans@apache.org
> > >wrote:
> > >
> > >> Basically, ZK simply needs the lowest latency to disk and network in
> > >> order to work reliably. It's not CPU intensive, and it's only memory
> > >> intensive if you are using tons of znodes (HBase doesn't).
> > >>
> > >
> >
>

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