On Mon, Jan 4, 2010 at 9:39 AM, TuX RaceR <[email protected]> wrote:
> ... > I am trying to have information to increase the performance of the two > access modes. > > I would expect that mode a) performance does not really depend on the > number of replicas in HDFS > but that mode b) speed depends on the number of replicas in HDFS. It has > been said previously that random read accesses are limited by the > performance of the disks. > Can I artificially boost standard disks by adding more replicas to improve > random reads? > > The amount of replication should have no effect on either access mode. Whether scanning or random-accessing, only one of the N replicas is accessed. We'll only go to the other versions if there is trouble accessing the first. So, more replicas will not change the performance profile. What do you need to improve? Are both scans and random-reads slow for you? You've seen the performance page up on the wiki (I'm sure you have). Nothing there helps? St.Ack
