Re: NameNode low on available disk space

[Andy Isaacson <ad...@cloudera.com>]

Moving from general@ to user@.  The general list is not for technical
questions, it's to discuss project-wide issues.

On Tue, Jan 22, 2013 at 1:03 PM, Mohit Vadhera
<pr...@gmail.com> wrote:
> Namenode switches into safemode when it has low disk space on the root fs /
> i have to manually run a command to leave it. Below are log messages for
> low space on root / fs. Is there any parameter so that i can reduce
> reserved amount.
>
> 2013-01-21 01:22:52,217 WARN
> org.apache.hadoop.hdfs.server.namenode.NameNodeResourceChecker: Space
> available on volume '/dev/mapper/vg_lv_root' is 10653696, which is below
> the configured reserved amount 104857600
> 2013-01-21 01:22:52,218 WARN
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem: NameNode low on
> available disk space. Entering safe mode.
> 2013-01-21 01:22:52,218 INFO org.apache.hadoop.hdfs.StateChange: STATE*
> Safe mode is ON.

If your Namenode filesystem really only has 10MB available, you are
running well into a red zone for data loss. You cannot safely operate
a NN when the filesystem is that close to being out of space and going
to safemode is appropriate.

The default reserve of 100MB is a good margin of safety for a small
cluster. Instead of decreasing your safety margin, fix your machine so
that there is more than 100MB available on the NN filesystem.

-andy