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Posted to common-user@hadoop.apache.org by Torsten Curdt <tc...@apache.org> on 2008/07/30 20:09:15 UTC
corrupted fsimage and edits
Just a bit of a feedback here.
One of our hadoop 0.16.4 namenodes had gotten a disk full incident
today. No second backup namenode was in place. Both files fsimage and
edits seem to have gotten corrupted. After quite a bit of debugging
and fiddling with a hex edtor we managed to resurrect the files and
continue with just minor loss.
Thankfully this only happened on a development cluster - not on
production. But shouldn't that be something that should NEVER happen?
cheers
--
Torsten
Re: corrupted fsimage and edits
Posted by Konstantin Shvachko <sh...@yahoo-inc.com>.
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.
http://wiki.apache.org/hadoop/FAQ#7
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.
--Konstantin
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
>
>
Re: corrupted fsimage and edits
Posted by Raghu Angadi <ra...@yahoo-inc.com>.
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
Re: corrupted fsimage and edits
Posted by Torsten Curdt <tc...@apache.org>.
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.
> 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
Re: corrupted fsimage and edits
Posted by Raghu Angadi <ra...@yahoo-inc.com>.
You should always have more than one location (preferably on different
disks) for fsimage and editslog.
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.
Raghu.
Torsten Curdt wrote:
> Just a bit of a feedback here.
>
> One of our hadoop 0.16.4 namenodes had gotten a disk full incident
> today. No second backup namenode was in place. Both files fsimage and
> edits seem to have gotten corrupted. After quite a bit of debugging and
> fiddling with a hex edtor we managed to resurrect the files and continue
> with just minor loss.
>
> Thankfully this only happened on a development cluster - not on
> production. But shouldn't that be something that should NEVER happen?
>
> cheers
> --
> Torsten