Home | About | Sematext search-lucene.com search-hadoop.com
 Search Hadoop and all its subprojects:

Switch to Threaded View
MapReduce >> mail # user >> Question about writing HDFS files

Copy link to this message
Re: Question about writing HDFS files
That is not true. HDFS writes are not staged to a local disk first
before being written onto the DataNodes. The old architecture docs
seem to suggest that the writes get staged to a local disk but thats
not true anymore, see https://issues.apache.org/jira/browse/HDFS-1454.

Also worth noting that a HDFS client behaves the same way in almost
all contexts, whether its invoked from an MR framework or directly
from shell.

On Fri, May 17, 2013 at 3:38 AM, John Lilley <[EMAIL PROTECTED]> wrote:
> I seem to recall reading that when a MapReduce task writes a file, the
> blocks of the file are always written to local disk, and replicated to other
> nodes.  If this is true, is this also true for non-MR applications writing
> to HDFS from Hadoop worker nodes?  What about clients outside of the cluster
> doing a file load?
> Thanks
> John

Harsh J