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HBase, mail # user - HBase failure scenarios


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Re: HBase failure scenarios
Azuryy Yu 2013-06-11, 07:27
yes,
when a write is successful to the WAL on the responsible region server,
in fact that means that the write was committed to 3 total DataNodes

--Send from my Sony mobile.
On Jun 11, 2013 8:40 AM, "Lucas Stanley" <[EMAIL PROTECTED]> wrote:

> Thanks Azuryy!
>
> So, when a write is successful to the WAL on the responsible region server,
> in fact that means that the write was committed to 3 total DataNodes,
> correct?
>
>
> On Mon, Jun 10, 2013 at 5:37 PM, Azuryy Yu <[EMAIL PROTECTED]> wrote:
>
> > yes. datanode write is pipeline. and only if pipeline writing finished,
> dn
> > return ok.
> >
> > --Send from my Sony mobile.
> > On Jun 11, 2013 8:27 AM, "Lucas Stanley" <[EMAIL PROTECTED]> wrote:
> >
> > > Hi,
> > >
> > > In the Strata 2013 training lectures, Jonathan Hsieh from Cloudera said
> > > something about HBase syncs which I'm trying to understand further.
> > >
> > > He said that HBase sync guarantees only that a write goes to the local
> > disk
> > > on the region server responsible for that region and in-memory copies
> go
> > on
> > > 2 other machines in the HBase cluster.
> > >
> > > But I thought that when the write goes to the WAL on the first region
> > > server, that the HDFS append would push that write to 3 machines total
> in
> > > the HDFS cluster. In order for the append write to the WAL to be
> > > successful, doesn't the DataNode on that machine have to pipeline the
> > write
> > > to 2 other DataNodes?
> > >
> > > I'm not sure what Jonathan was referring to when he said that 2
> in-memory
> > > copies go to other HBase machines? Even when the memstore on the first
> > > region server gets full, doesn't the flush to the HFile get written on
> 3
> > > HDFS nodes in total?
> > >
> >
>