Grokbase Groups Pig user July 2011
ok then

1. We have to write a pig job for merging or PIG itself merges so that less number of mappers are invoked.

2. Can we copy to a cluster from a non cluster machine, using the namespace URI of the NN ? - We can dedicate some good config boxes to do our merging and copying and then copy it to NN over network.

3. How is the performance of FileCrusher tool ?

We found that to copy 12 GB of data for all the 15 apps in parallel took 35 mins.

we ran 15 copy from local each having 12 GB data.


From: Dmitriy Ryaboy <>
To:; jagaran das <>
Sent: Saturday, 16 July 2011 7:58 AM
Subject: Re: Hadoop Production Issue

Merging: doesn't actually speed things up all that much; reduces load
on the Namenode, and speeds up job initialization some. You don't have
to do it on the namenode itself. Neither do you have to do copying on
the NN. In fact, don't do anything but run the NameNode on the

Pig jobs can transparently merge small jobs into larger chunks, so you
won't be stuck with 11K mappers.

Don't copy to local an then run SQL loader. Use Sqoop export, and load
directly from Hadoop.

You cannot append to a file that already exists in the cluster. This
will be available in one of the coming Hadoop releases. You can
certainly create a new file in a directory, and load whole

On Sat, Jul 16, 2011 at 1:17 AM, jagaran das wrote:


Due to requirements in our current production CDH3 cluster we need to copy around 11520 small size files (Total Size 12 GB) to the cluster for one application.
Like this we have 20 applications that would run in parallel

So one set would have 11520 files of total size 12 GB
Like this we would have 15 sets in parallel,

We have a total SLA for the pipeline from copy to pig aggregation to copy to local and sql load is 15 mins.

What we do:

1. Merge Files so that we get rid of small files. - Huge time hit process??? Do we have any other option???
2. Copy to cluster
3. Execute PIG job
4. copy to local
5 Sql loader

Can we perform merge and copy to cluster from a different host other than the Namenode?
We want an out of cluster machine running a java process that would
1. Run periodically
2. Merge Files
3. Copy to Cluster

If we can append to an existing file in cluster?

Please provide your thoughts as maintaing the SLA is becoming tough.


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postedJul 15, '11 at 7:41p
activeJul 17, '11 at 4:25a



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