hbase-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From anil gupta <anilgupt...@gmail.com>
Subject Re: persistence in Hbase
Date Fri, 11 Jan 2013 04:22:16 GMT
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 <anilgupta84@gmail.com> 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 <larsh@apache.org> 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 <anilgupta84@gmail.com>
>> To: user@hbase.apache.org
>> 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 <mohitanchlia@gmail.com
>> >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 <
>> > ramkrishna.s.vasudevan@gmail.com> 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 <panshul007@gmail.com>
>> > > 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

Mime
  • Unnamed multipart/alternative (inline, None, 0 bytes)
View raw message