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From Vitalii Tymchyshyn <tiv...@gmail.com>
Subject Re: Timer jobs
Date Fri, 02 Sep 2011 07:15:00 GMT
01.09.11 21:55, Per Steffensen написав(ла):
> Vitalii Tymchyshyn skrev:
>> Hello.
>> AFAIK now you still have HDFS NameNode and as soon as NameNode is 
>> down - your cluster is down. So, putting scheduling on the same 
>> machine as NameNode won't make you cluster worse in terms of SPOF (at 
>> least for HW failures).
>> Best regards, Vitalii Tymchyshyn
> I believe this is why there is also a secondary namenode. 


Not at all. Secondary name node is not even a hot standby. You HDFS 
cluster address is namenode:port and no one who connects with it knows 
about secondary name node, so it's not a HA solution.
AFAIR secondary name node even is not a backup, but simply a tools to 
help main name node to process transaction logs at a scheduled fashion. 
0.21 has backup name node, but 0.21 is unstable and it's backup node 
does not work (tried it). For 0.20 the backup solution mentioned in the 
docs is to have a NFS mount on name node and specify it as a secondary 
name node data directory.

Best regards, Vitalii Tymchyshyn.

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