Never mind i got the Jira: https://issues.apache.org/jira/browse/HBASE-5954
On Thu, Jan 10, 2013 at 8:16 PM, anil gupta <[email protected]> wrote: > Hi Lars, > > Yes, that is true. I also came to know about it few days ago that data is > present in Memory(rather than persistent storage) of 3 DataNode if the > replication factor is 3. In case of disaster like entire data center > failure there might be some data loss. But these kinds of disaster are very > rare at Enterprise clusters.(I am only worried about data loss in prod) In > a normal failure of 1-2 node in cluster we would not loose any data due to > WAL. The probability of data loss increases by a large amount when WAL is > off. Is there any JIRA in HBase for utilizing HDFS-744? It would be great > to have this feature in HBase. > > Thanks, > Anil Gupta > > > On Thu, Jan 10, 2013 at 7:54 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 >> >> > > > -- > Thanks & Regards, > Anil Gupta > -- Thanks & Regards, Anil Gupta
