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HBase >> mail # user >> Re: persistence in Hbase


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Re: persistence in Hbase
Hi,

Just for my own edification - isn't data loss always going to be possible
due to caches present in HDDs and inability(?) for force them to flush.  I
believe I've read even fsync lies...

Thanks,
Otis
--
HBASE Performance Monitoring - http://sematext.com/spm/index.html

On Thu, Jan 10, 2013 at 10:54 PM, lars hofhansl <[EMAIL PROTECTED]> wrote:

> Not entirely true, though.
> Data is not sync'ed to disk, but only distributed to all HDFS replicas.
> During a power outage event across all HDFS failure zones (such as a data
> center) you can lose data.
>
>
> -- Lars
>
>
>
> ----- Original Message -----
> From: anil gupta <[EMAIL PROTECTED]>
> To: [EMAIL PROTECTED]
> Cc:
> Sent: Thursday, January 10, 2013 2:38 PM
> Subject: Re: persistence in Hbase
>
> Hi Mohammad,
>
> If the Write Ahead Log(WAL) is "turned on" then in **NO** case data should
> be lost. HBase is strongly-consistent. If you know of any case when WAL is
> turned on and data is lost then IMO that's a Critical bug in HBase.
>
> Thanks,
> Anil Gupta
>
> On Thu, Jan 10, 2013 at 7:37 AM, Mohit Anchlia <[EMAIL PROTECTED]
> >wrote:
>
> > Data also gets written in WAL. See:
> >
> > http://hbase.apache.org/book/perf.writing.html
> >
> > On Thu, Jan 10, 2013 at 7:36 AM, ramkrishna vasudevan <
> > [EMAIL PROTECTED]> wrote:
> >
> > > Yes definitely you will get back the data.
> > >
> > > Please read the HBase Book that explains things in detail.
> > > http://hbase.apache.org/book.html.
> > >
> > > Regards
> > > Ram
> > >
> > >
> > > On Thu, Jan 10, 2013 at 8:48 PM, Panshul Gupta <[EMAIL PROTECTED]>
> > > wrote:
> > >
> > >  > Hello,
> > > >
> > > > I was wondering if it is possible that I have data stored in Hbase
> > tables
> > > > on my 10 node cluster. I switch off (power down) my cluster. When I
> > power
> > > > up my cluster again, and run the HDFS and hadoop daemons, will the
> > Hbase
> > > > have my old data persisted in the form I left it?? or will I have to
> re
> > > > import all the data??
> > > >
> > > > Thankyou for the help.
> > > >
> > > > --
> > > > Regards,
> > > > Panshul.
> > > > http://about.me/panshulgupta
> > > >
> > >
> >
>
>
>
> --
> Thanks & Regards,
> Anil Gupta
>
>
NEW: Monitor These Apps!
elasticsearch, apache solr, apache hbase, hadoop, redis, casssandra, amazon cloudwatch, mysql, memcached, apache kafka, apache zookeeper, apache storm, ubuntu, centOS, red hat, debian, puppet labs, java, senseiDB