hadoop-hdfs-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Sugandha Naolekar <sugandha....@gmail.com>
Subject Re: Mappers vs. Map tasks
Date Tue, 25 Feb 2014 06:05:56 GMT
One more thing to ask: No. of blocks = no. of mappers. Thus, those many no.
of times the map() function will be called right?

--
Thanks & Regards,
Sugandha Naolekar





On Tue, Feb 25, 2014 at 11:27 AM, Sugandha Naolekar
<sugandha.n87@gmail.com>wrote:

> Hello,
>
> As per the various articles I went through till date, the File(s) are
> split in chunks/blocks. On the same note, would like to ask few things:
>
>
>    1. No. of mappers are decided as: Total_File_Size/Max. Block Size.
>    Thus, if the file is smaller than the block size, only one mapper will be
>    invoked. Right?
>    2. If yes, it means, the map() will be called only once. Right? In
>    this case, if there are two datanodes with a replication factor as 1: only
>    one datanode(mapper machine) will perform the task. Right?
>    3. The map() function is called by all the datanodes/slaves right? If
>    the no. of mappers are more than the no. of slaves, what happens?
>
> --
> Thanks & Regards,
> Sugandha Naolekar
>
>
>
>

Mime
View raw message