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From Harsh J <ha...@cloudera.com>
Subject Re: Lzo vs SequenceFile for big file
Date Mon, 10 Sep 2012 04:40:09 GMT
A few things:

Storing simple, singular text records into sequence files isn't
optimal, as you're just adding overheads for every line of text stored
as Text type in it. If you have typed data and can benefit from
type-based serializations for each record, go for a container format
like SequenceFiles (With whatever serialization technique) or Avro
DataFiles (Has embedded schema support, among other niceties).

When comparing the result with Lzo, also factor in the indexing time
as thats part of the requirement in making it parallel (I think the
newer libs auto-index, but thats just what I heard was the plan, dunno
if its already available).

On Fri, Sep 7, 2012 at 4:55 AM, Young-Geun Park
<younggeun.park@gmail.com> wrote:
> Hi, All
>
> I have tested which method is better between Lzo and SequenceFile for a BIG
> file.
>
> File size is 10GiB and WordCount MR is used.
> Inputs of WordCount MR are  lzo which would be indexed by LzoIndexTool(lzo),
> sequence file which is compressed by block level snappy(seq)  , and
> uncompressed original file(none).
>
> Map output  is compressed except of uncompressed file. mapreduce output is
> not compressed for all cases.
>
> The following are wordcount MR running time;
> none       lzo         seq
> 248s      243s     1410s
>
> -Test Environments
>
> OS : CentOS 5.6 (x64) (kernel = 2.6.18)
> # of Core  : 8 (cpu = Intel(R) Xeon(R) CPU E5504  @ 2.00GHz)
> RAM : 18GB
> Java version : 1.6.0_26
> Hadoop version : CDH3U2
> # of datanode(tasktracker) :  8
>
> According to the result, The running time of SequnceFile is much less than
> the others.
> Before testing, I had expected that the results of  both SequenceFile and
> Lzo are about the same.
>
> I want to know why performance of the sequence file compressed by snappy is
> so bad?
>
> do I miss anything in tests?
>
>
> Regards,
> Park
>
>



-- 
Harsh J

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