You are right. The software should not get a free pass only because the hardware might lose data, though. :)
________________________________ From: Otis Gospodnetic <[email protected]> To: [email protected]; lars hofhansl <[email protected]> Sent: Monday, January 14, 2013 7:19 PM Subject: 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 > >
