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From Todd Lipcon <t...@cloudera.com>
Subject Re: Name Node Corruption When Shutdown Too Soon
Date Wed, 10 Feb 2010 01:27:15 GMT
Hi Jonathan,

I've reproduced your issue.

I'll comment on HDFS-955 as I believe this is another manifestation of
the same issue.

-Todd

On Tue, Feb 9, 2010 at 12:11 PM, Todd Lipcon <todd@cloudera.com> wrote:
> Thanks Jonathan,
>
> I tried to reproduce this yesterday using a single dfs.name.dir, but
> I'll give it a go again with multiple.
>
> Will let you know what I turn up.
>
> -Todd
>
> On Tue, Feb 9, 2010 at 12:05 PM, Allen, Jonathan <jonathan.allen2@hp.com> wrote:
>> Todd,
>>
>> Unfortunately my test system is air gapped away from the internet so I haven't been
able to transfer my test case across yet but the basic steps as are follows:
>>
>> 1) start-dfs (also shutdown the secondary to make sure that it didn't checkpoint
away the edit log)
>> 2) create lots of small files so that there is a large edit log (I created about
4,500 files resulting in an edit log of just over 1MB).
>> 3) stop-dfs
>> 4) start-dfs
>> 5) wait for name node to start reading the edit log but not long enough for it to
finish reading it (I waited for a couple of seconds).
>> 6) stop-dfs
>> 7) start-dfs
>> 8) listing the hdfs directory now shows it in the same state as at step (1) rather
than the correct state as at step (3).
>>
>> This was running with the Yahoo distro of 0.20.1.
>>
>> The dfs.name.dir is configured to use directories on 2 local drives and 1 NFS mounted
drive.
>>
>> Thanks,
>> Jonathan
>>
>> Jonathan Allen
>> UKGP, NS&R, Defence and Security
>> HP Enterprise Services
>> Telephone +44 1682 292101
>> Email jonathan.allen.uk@hp.com
>> Street address, Unit 29, Alexandra Way, Ashchurch Business Park, Tewkesbury, Gloucestershire.
GL20 8NB
>>
>> Hewlett-Packard Limited registered Office: Cain Road, Bracknell, Berks RG12 1HN
>> Registered No: 690597 England
>> The contents of this message and any attachments to it are confidential and may be
legally privileged. If you have received this message in error, you should delete it from
your system immediately and advise the sender.
>> To any recipient of this message within HP, unless otherwise stated you should consider
this message and attachments as "HP CONFIDENTIAL".
>>
>>
>> -----Original Message-----
>> From: Todd Lipcon [mailto:todd@cloudera.com]
>> Sent: 09 February 2010 01:11
>> To: hdfs-dev@hadoop.apache.org
>> Subject: Re: Name Node Corruption When Shutdown Too Soon
>>
>> Hi Jonathan,
>>
>> Another question: how have you configured dfs.name.dir? Do you have
>> several directories configured?
>>
>> Thanks
>> -Todd
>>
>> On Mon, Feb 8, 2010 at 4:45 PM, Todd Lipcon <todd@cloudera.com> wrote:
>>> Hey Jonathan,
>>>
>>> As Konstantin mentioned, I've been looking into a couple issues that
>>> could be related. At first glance it doesn't sound like you've run
>>> into quite the same thing.
>>>
>>> What version did you see this on? The steps to reproduce are something like:
>>>
>>> 1) Start a NN
>>> 2) Perform a bunch of edits so there is a large edit log
>>> 3) kill -9 the NN
>>> 4) start the NN again
>>> 5) while it is in the middle of replaying edits, kill -9 it again
>>> 6) start the NN, and lose all the previous edits?
>>>
>>> Or did I misunderstand what happened? If that sounds right, I'll give
>>> it a go and see if I can reproduce.
>>>
>>> Thanks
>>> -Todd
>>>
>>> On Sun, Feb 7, 2010 at 8:45 AM, Allen, Jonathan <jonathan.allen2@hp.com>
wrote:
>>>> I've come across a name node bug and just wanted to check if it's a known
issue before I formally raise it (I've had a quick look through the database but couldn't
see anything obvious).
>>>>
>>>> If the name node is shut down before it has completed reading through the
edit log then the edit log gets removed without the image file being updated.  This results
in name node reverting to its previously saved state (out of sync with the data nodes) and
the most recent edits getting lost.
>>>>
>>>> Does anybody recognise this as a known issue or should I raise it?
>>>>
>>>> Thanks,
>>>> Jonathan Allen
>>>> UKGP, NS&R, Defence and Security
>>>> HP Enterprise Services
>>>> Telephone +44 1682 292101
>>>> Email jonathan.allen.uk@hp.com
>>>> Street address, Unit 29, Alexandra Way, Ashchurch Business Park, Tewkesbury,
Gloucestershire. GL20 8NB
>>>>
>>>> Hewlett-Packard Limited registered Office: Cain Road, Bracknell, Berks RG12
1HN
>>>> Registered No: 690597 England
>>>> The contents of this message and any attachments to it are confidential and
may be legally privileged. If you have received this message in error, you should delete it
from your system immediately and advise the sender.
>>>> To any recipient of this message within HP, unless otherwise stated you should
consider this message and attachments as "HP CONFIDENTIAL".
>>>>
>>>>
>>>>
>>>>
>>>
>>
>

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