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.
