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From viva v <vivamail...@gmail.com>
Subject Re: Newbie question on block size calculation
Date Thu, 23 Feb 2012 11:43:19 GMT
```Thanks very much for the clarification.

So, we'd i guess ideally set the block size equal to the transfer rate for
optimum results.

If seek time has to be 0.5% of transfer time would i set my block size at
200MB (higher than transfer rate)?
Conversely if seek time has to be 2% of transfer time would i still set my
block size at 100MB?

On Wed, Feb 22, 2012 at 8:16 PM, Praveen Sripati
<praveensripati@gmail.com>wrote:

> Seek time is ~ 10ms. If seek time has to be 1% of the transfer time then
> transfer time has to be ~ 1000 ms (1s).
>
> In ~ 1000 ms (1s) with a transfer rate of 100 MB/s, a block of 100MB can
>
> Praveen
>
> On Wed, Feb 22, 2012 at 11:22 AM, viva v <vivamailers@gmail.com> wrote:
>
>> Have just started getting familiar with Hadoop & HDFS. Reading Tom
>> White's book.
>>
>> The book describes an example related to HDFS block size. Here's a
>> verbatim excerpt from the book
>>
>> "If the seek time is around 10 ms, and the transfer rate is 100 MB/s,
>> then to make the seek time 1% of the transfer time, we need to make the
>> block size around 100 MB."
>>
>> I can't seem to understand how we arrived at the fact that block size
>> shold be 100MB.
>>