Hi Todd The Node comprises of multi disk (7 to be precise), and there are 6 data nodes.
The measurement used is that provided by TestDFSIO which comes with hadoop*test.jar With the defined block size of 128 MB 44 files of 120 MB was written giving an throughput of 90MB/s 44 files of 100MB gave a read throughput of 30 MB/s The problem is how do I conclude and compare these numbers with raw disk read throughputs Regards Rohan Todd Lipcon wrote:
Hi Rohan, How are you measuring throughput? The throughput from a single client will not scale up as the cluster size increases, as it does not parallelize reads across multiple nodes. Of course it will also be limited by the inbound bandwidth of that node. -Todd On Fri, May 14, 2010 at 1:23 AM, Rohan Rai <rohan....@inmobi.com <mailto:rohan....@inmobi.com>> wrote: Hi Is there a relationship between HDFS Read throught put and Disk Read throughput. If yes what would be that. Lets say we have a disk giving us 120 MB/s And a Cluster of 6 Nodes Each Node having 6 disk. So in an absolutely ideal world it should give us a through put of 120*6*6 MB/s if used in parallel In a non ideal world we can divide above by a factor of x Then why is that the general CLUSTER read throughput is so very less. Generally it hovers around 90MB/s. How is the throughput which cluster provides is accounted for. Just for information, configs are , 8 GB RAM, 250 GB HDD, 8 Maps per node, 128 Kb Block size Regards Rohan The information contained in this communication is intended solely for the use of the individual or entity to whom it is addressed and others authorized to receive it. It may contain confidential or legally privileged information. If you are not the intended recipient you are hereby notified that any disclosure, copying, distribution or taking any action in reliance on the contents of this information is strictly prohibited and may be unlawful. If you have received this communication in error, please notify us immediately by responding to this email and then delete it from your system. The firm is neither liable for the proper and complete transmission of the information contained in this communication nor for any delay in its receipt. -- Todd Lipcon Software Engineer, Cloudera
The information contained in this communication is intended solely for the use of the individual or entity to whom it is addressed and others authorized to receive it. It may contain confidential or legally privileged information. If you are not the intended recipient you are hereby notified that any disclosure, copying, distribution or taking any action in reliance on the contents of this information is strictly prohibited and may be unlawful. If you have received this communication in error, please notify us immediately by responding to this email and then delete it from your system. The firm is neither liable for the proper and complete transmission of the information contained in this communication nor for any delay in its receipt.
