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From Harsh J <ha...@cloudera.com>
Subject Re: HDFS Backup nodes
Date Thu, 08 Dec 2011 01:32:29 GMT
Randy,

On recent releases (CDH3u2 here for example), you also have
"dfs.name.dir.restore", a boolean flag that will automatically try to
enable previously failed name directories upon every checkpoint if
possible. Hence if you have a SNN running, and your NFS failed at some
point and got marked as FAILED on your NN web UI, if the NFS is back
up again before the next checkpoint interval, it will be auto-restored
after the NN deems its in a writable state again.

On Thu, Dec 8, 2011 at 6:00 AM, randy <randysch@comcast.net> wrote:
> Thanks Joey. We've had enough problems with nfs (mainly under very high
> load) that we thought it might be riskier to use it for the NN.
>
> randy
>
>
> On 12/07/2011 06:46 PM, Joey Echeverria wrote:
>>
>> Hey Rand,
>>
>> It will mark that storage directory as failed and ignore it from then
>> on. In order to do this correctly, you need a couple of options
>> enabled on the NFS mount to make sure that it doesn't retry
>> infinitely. I usually run with the tcp,soft,intr,timeo=10,retrans=10
>> options set.
>>
>> -Joey
>>
>> On Wed, Dec 7, 2011 at 12:37 PM,<randysch@comcast.net>  wrote:
>>>
>>> What happens then if the nfs server fails or isn't reachable? Does hdfs
>>> lock up? Does it gracefully ignore the nfs copy?
>>>
>>> Thanks,
>>> randy
>>>
>>> ----- Original Message -----
>>> From: "Joey Echeverria"<joey@cloudera.com>
>>> To: common-user@hadoop.apache.org
>>> Sent: Wednesday, December 7, 2011 6:07:58 AM
>>> Subject: Re: HDFS Backup nodes
>>>
>>> You should also configure the Namenode to use an NFS mount for one of
>>> it's storage directories. That will give the most up-to-date back of
>>> the metadata in case of total node failure.
>>>
>>> -Joey
>>>
>>> On Wed, Dec 7, 2011 at 3:17 AM, praveenesh kumar<praveenesh@gmail.com>
>>>  wrote:
>>>>
>>>> This means still we are relying on Secondary NameNode idealogy for
>>>> Namenode's backup.
>>>> Can OS-mirroring of Namenode is a good alternative keep it alive all the
>>>> time ?
>>>>
>>>> Thanks,
>>>> Praveenesh
>>>>
>>>> On Wed, Dec 7, 2011 at 1:35 PM, Uma Maheswara Rao
>>>> G<maheswara@huawei.com>wrote:
>>>>
>>>>> AFAIK backup node introduced in 0.21 version onwards.
>>>>> ________________________________________
>>>>> From: praveenesh kumar [praveenesh@gmail.com]
>>>>> Sent: Wednesday, December 07, 2011 12:40 PM
>>>>> To: common-user@hadoop.apache.org
>>>>> Subject: HDFS Backup nodes
>>>>>
>>>>> Does hadoop 0.20.205 supports configuring HDFS backup nodes ?
>>>>>
>>>>> Thanks,
>>>>> Praveenesh
>>>>>
>>>
>>>
>>>
>>> --
>>> Joseph Echeverria
>>> Cloudera, Inc.
>>> 443.305.9434
>>
>>
>>
>>
>



-- 
Harsh J

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