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From Allen Wittenauer ...@apache.org>
Subject Re: namenode format error
Date Wed, 13 Apr 2011 21:07:47 GMT

On Apr 13, 2011, at 12:38 PM, Jeffrey Wang wrote:
> It's just in my home directory, which is an NFS mount. I moved it off NFS and it seems
to work fine. Is there some reason it doesn't work with NFS?


Locking on NFS--regardless of application--is a dice roll, especially when client/server are
different OSes and platforms.  Heck even when they are the same, it might not work.  For example,
on some older Linux kernels, flock() on NFS only created a lock locally and didn't tell the
NFS server, allowing another client to claim a lock!  (IIRC, fcntl did work...)

Best bet is to make sure rpc.lockd (or whatever daemon provides NFS locking) is running/working
and to use the highest compatible version of NFS.  NFSv4, in particular, has file locking
built into the protocol rather than as an 'external' service.
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