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From Konstantin Shvachko <...@yahoo-inc.com>
Subject Re: corrupted fsimage and edits
Date Wed, 30 Jul 2008 22:46:26 GMT
You should also run a secondary name-node, which does namespace checkpoints and shrinks the
edits log file.
And this is exactly the case when the checkpoint image comes handy.
In the recent release you can start the primary node using the secondary image directly.
In the old releases you need to move some files around.

Raghu Angadi wrote:
> Torsten Curdt wrote:
>> On Jul 30, 2008, at 20:35, Raghu Angadi wrote:
>>> You should always have more than one location (preferably on 
>>> different disks) for fsimage and editslog.
>> On production we do frequent backups. Is there a mechanism from inside 
>> hadoop now to do something like that now? The "more than one location" 
>> bit sounds a little like that.
> You can specify multiple directories for "dfs.name.dir", in which case 
> fsimage and editslog are written to multiple places. If one of these 
> goes bad, you can use the other one.
> See http://wiki.apache.org/hadoop/FAQ#15
> Raghu.
>>> A few months back I had a proposal to keep checksums for each record 
>>> on fsimage and editslog and NameNode would recover transparently from 
>>> such corruptions when there are more than one copies available. It 
>>> didn't come up in priority since there were no such failures observed.
>>> You should certainly report these cases and will help the feature 
>>> gain more traction.
>> Will file a bug report tomorrow.
>> cheers
>> -- 
>> Torsten

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