Hey Martin, It would be an interesting experiment but I'm not sure it would improve things as the host (and hardware to some extent) are already reading ahead. A useful exercise would be to evaluate whether the new default host parameters for on-demand readahead are suitable for hadoop.
http://lwn.net/Articles/235164 http://lwn.net/Articles/235181 Thanks, Eli On Mon, Nov 23, 2009 at 11:23 PM, Martin Mituzas <[email protected]> wrote: > > I read the code and find the call > DFSInputStream.read(buf, off, len) > will cause the DataNode read len bytes (or less if encounting the end of > block) , why does not hdfs read ahead to improve performance for sequential > read? > -- > View this message in context: > http://old.nabble.com/why-does-not-hdfs-read-ahead---tp26491449p26491449.html > Sent from the Hadoop core-user mailing list archive at Nabble.com. > >
