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From Fredrik Widlund <>
Subject RE: CouchDB and Hadoop_
Date Fri, 16 Apr 2010 15:22:20 GMT

Well, we're building a solution on Couch and replication on a relatively large scale and saying
"it just works" doesn't really describe it for us. I really like the Couch design but it's
a bit of a challenge making it work, for us. I can describe the case if you like.

Also we already have a decentralized distributed file system layer (which often is a natural
part of a cloud solution I suppose) so if we could run it on top of that it would lessen the
complexity of the overall solution.

In any case it was a quick comment to the Hadoop question, and maybe it just wouldn't work
that way. You could in general discuss atomic operations/locking and performance implications
by moving synchronization to a lower abstraction layer I guess.

Kind regards,
Fredrik Widlund

-----Original Message-----
From: Sebastian Cohnen []
Sent: den 16 april 2010 15:41
Subject: Re: CouchDB and Hadoop_

Why would someone possibly do that? CouchDB can do many things really well, and replication
is one of these things. It's dead simple to set up and just works...

On 16.04.2010, at 15:29, Fredrik Widlund wrote:

> Are the files reopened for each write etc? If locking works glusterfs for example could
be a nice solution for the replication. Each write would be atomically written to all instances,
and reads would be local (using AFR with preferred servers).
> Kind regards,
> Fredrik Widlund
> -----Original Message-----
> From: Suhail Ahmed []
> Sent: den 16 april 2010 10:13
> To:
> Subject: Re: CouchDB and Hadoop
> Sure It can be done but for me the whole Java to Erlang layer would be a
> mess since they are so different. The better way to go about doing this
> would to be implement a distributed file system like Hadoop underneath Couch
> for same effect.
> On Fri, Apr 16, 2010 at 1:16 AM, Steve-Mustafa Ismail Mustafa <
>> wrote:
>> I swear, I spent over an hour going through the mailing list trying to find
>> an answer.
>> I know that CouchDB is a document oriented DB and I know that Hadoop is a
>> File System and that both implement Map/Reduce.  But is it possible to have
>> them stacked with Hadoop being the FS in use and CouchDB being the DB? This
>> way, wouldn't you get the distributed/clustered FS abilities of Hadoop in
>> addition to the powerful retrieval abilities of CouchDB?
>> If its not possible, and I suspect that it is so, _why_? Don't they operate
>> on two seperate levels? Wouldn't CouchDB sort of replace HBase?
>> Thanks in advance for any and all replies

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