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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-370) TaskTracker startup fails if any mapred.local.dir entries don't exist
Date Thu, 20 Jul 2006 09:44:18 GMT
    [ http://issues.apache.org/jira/browse/HADOOP-370?page=comments#action_12422378 ] 
            
Doug Cutting commented on HADOOP-370:
-------------------------------------

Yes, let's cache the "good dirs".  If a drive goes offline or becomes unwritable while a node
is running, then we should start emitting warnings, but we should not warn more than once
for drives that are offline or unwritable at startup.

> TaskTracker startup fails if any mapred.local.dir entries don't exist
> ---------------------------------------------------------------------
>
>                 Key: HADOOP-370
>                 URL: http://issues.apache.org/jira/browse/HADOOP-370
>             Project: Hadoop
>          Issue Type: Bug
>          Components: mapred
>         Environment: ~30 node cluster, various size/number of disks, CPUs, memory
>            Reporter: Bryan Pendleton
>         Attachments: fix-freespace-tasktracker-failure.txt
>
>
> This appears to have been introduced with the "check for enough free space" before startup.
> It's debatable how best to fix this bug. I will submit a patch which ignores directories
for which the DF utility fails. This is letting me continue operation on my cluster (where
the number of drives varies, so there are entries in mapred.local.dir for drives that aren't
on all cluster nodes), but a cleaner solution is probably better. I'd lean towards "check
for existence", and ignore the dir if it doesn't  - but don't depend on DF to fail, since
DF could fail for other reasons without meaning you're out of disk space. I argue that a TaskTracker
should start up if *all* directories that *can be written to* in the list have enough space.
Otherwise, a failed drive per cluster machine means no work ever gets done.

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