Vitalii Tymchyshyn skrev:
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.
Hello.
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.
Hmm, then I believe Hadoop has a serious HA problem built-in. That is
not so smart when most of it is about doing HA. But I guess work is
going on to solve that - in 0.21 and further forward. But thanks for you
explanation.
Regards, Per Steffensen
