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From Brian Bockelman <bbock...@cse.unl.edu>
Subject Re: Does Hadoop 0.20.2 and HBase 0.90.3 compatible ??
Date Fri, 03 Jun 2011 12:23:16 GMT
A meta-comment here (triggered by Praveenesh's comments about not wanting to re-install):

If you have to install the same software on more than one piece of software, you really ought
to automate it.  In the long run, you'll save more time if you can instantly roll out changes
than manually doing it.  In all likelihood, if you're going to be working with a piece of
software (Hadoop-based or not!), you'll re-install it a few times.

The install of HDFS should take roughly the same amount of time on 2, 20, or 200 nodes.


On Jun 3, 2011, at 6:47 AM, Andrew Purtell wrote:

>> Is *Hadoop 0.20.2  also not compatible with Hbase 0.90.3 ???*
> In a strict sense they are, but without append support HBase cannot guarantee that the
last block of write ahead logs are synced to disk, so in some failure cases edits will be
lost. With append support then the "hole" of these failure cases is closed. Also append branch
adds a change to lease recovery that allows the HBase Master to take ownership of regionserver
logs in order to split them quickly. (Without this patch you may be waiting 10 minutes for
lease recovery...) So these differences are clearly important for durability and fault recovery
in a realistic time frame.
> A full reinstallation is not necessary.
> You can take the Hadoop core jar packaged in lib/ of HBase 0.90.3 and replace every Hadoop
core jar on your cluster with them.
> OR 
> You can compile 0.20-append and just replace the Hadoop core jar everywhere with the
result, including the one in the HBase lib/.
>   - Andy
> --- On Fri, 6/3/11, praveenesh kumar <praveenesh@gmail.com> wrote:
>> From: praveenesh kumar <praveenesh@gmail.com>
>> Subject: Does Hadoop 0.20.2 and HBase 0.90.3 compatible ??
>> To: common-user@hadoop.apache.org, user@hbase.apache.org
>> Date: Friday, June 3, 2011, 3:37 AM
>> Guys,
>> I am in a very big big confusion. Please.. I really need
>> your feedbacks and
>> suggestions..
>> The scenario is like this...
>> I set up *Hadoop 0.20.2 cluster* of *12 nodes*..
>> Now I set up* Hbase 0.90.3*  *12 node cluster* on top
>> of it.
>> But after all that experimenting and struggling.. I read
>> the following SHOCKING line on my Hbase web UI
>> ---* " You are currently running the HMaster without HDFS append support
>> enabled. This may result in data loss. Please see the HBase wiki for
>> details. "*
>> And when I searched more about it.. I found Michael G. Nolls article..
>> saying that *Hadoop 0.20.2 and Hbase 0.90.2 are not compatible*.
>> Is *Hadoop 0.20.2  also not compatible with Hbase 0.90.3 ???*
>> So does  it means I have to re-install hadoop 0.20.
>> append if I want to use Hbase.
>> I did a lot of struggle to reach upto this stage.. do I
>> have to do all of it again.. ??
>> Is there any other work around solution.. of not
>> re-installing everything again ??
>> Please help..!!!  :-(
>> Thanks,
>> Praveenesh

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