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From: Apache Wiki <wikidiffs@apache.org>
To: Apache Wiki <wikidiffs@apache.org>
Date: Wed, 10 Jul 2013 19:12:04 -0000
Message-ID: <20130710191204.7625.99869@eos.apache.org>
Subject: 
 =?utf-8?q?=5BHadoop_Wiki=5D_Update_of_=22HadoopIsNot=22_by_SteveLoughran?=
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The "HadoopIsNot" page has been changed by SteveLoughran:
https://wiki.apache.org/hadoop/HadoopIsNot?action=3Ddiff&rev1=3D9&rev2=3D10

Comment:
clarify the FS a bit more

   * What the various log files your machine generates, and what they mean
   * How to set up native filesystems and mount them
  =

- This is important. If you don't know these, you are out of your depth and=
 should not start installing Hadoop until you have the basics of a couple o=
f linux systems up and running, letting you ssh in to each of them without =
entering a password, know each other's hostname and such like. The Hadoop i=
nstallation documents all assume you can do these things, and aren't going =
to bother explaining about them.
+ This is important. If you don't know these, you are out of your depth and=
 should not start installing Hadoop until you have the basics of a couple o=
f Linux systems up and running, letting you ssh in to each of them without =
entering a password, know each other's hostname and such like. The Hadoop i=
nstallation documents all assume you can do these things, and aren't going =
to bother explaining about them.
  =

  =

- =3D=3D HDFS is not a POSIX filesystem =3D=3D
+ =3D=3D HDFS is not a complete POSIX filesystem =3D=3D
  =

- The Posix filesystem model has files that can appended too, seek() calls =
made, files locked.You cannot seamlessly map code that assumes that all fil=
esystems are Posix-compatible to HDFS.
+ The Posix filesystem model has expectations of what a filesystem can do t=
hat HDFS cannot. A key one is that you can only add data to the end of the =
file, not seek to the middle and write things. You cannot seamlessly map co=
de that assumes that all filesystems are Posix-compatible to HDFS.
 =20