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From stu24m...@yahoo.com
Subject Re: HDFS Read ThroughPut and DISK Read ThroughPut
Date Fri, 14 May 2010 23:50:11 GMT
As a random, but related aside, there's a nice blog entry on yahoo's dev hadoop blog page.
It's all about throughput and scaling your cluster, etc. 

Take care,
-stu

Sent from my Verizon Wireless BlackBerry

-----Original Message-----
From: Rohan Rai <rohan.rai@inmobi.com>
Date: Fri, 14 May 2010 23:23:00 
To: hdfs-user@hadoop.apache.org<hdfs-user@hadoop.apache.org>
Subject: Re: HDFS Read ThroughPut and DISK Read ThroughPut

In addendum the cluster invokes the max of 44 Maps at a time

Regards
Rohan

Rohan Rai wrote:
> 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.rai@inmobi.com
>> <mailto:rohan.rai@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
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>>     this information is strictly prohibited and may be unlawful. If
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>>
>>
>>
>>
>> --
>> 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
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are hereby notified that any disclosure, copying, distribution or taking any action in reliance
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