start > CentOS > 5 > NFS File Creation Cache Problems
NFS File Creation Cache Problems
Problem
If I create a file on an nfs-mounted filesystem on one machine, the file may not be immediately visible to another machine looking at the same nfs-mounted filesystem.In our case this happened with a compute farm environment, where a job was dispatched to a remote machine to write some file, then when that job finished the dispatching machine tried immediately read that file. This would regularly fail and the immediate work-around was a sleep(10) step in between the dispatched-job-finish and the subsequent read-the-created-file step.Solution
$ man nfs
[...] lookupcache=type
This option dictates how directories and files should be cached when they are
accessed -- i.e. "looked up" -- on the server. A lookup can be either positive
(directory/file was found) or negative (directory/file was not found); both types
of lookups can be cached. By default, both positive and negative lookups are cached ( lookupcache=all ).
lookupcache=pos prevents negative lookups from being cached, while lookupcache=none
prevents all lookups from being cached. Note: lookupcache=none can adversely affect performance, but may be necessary if
shared files created or deleted on the server need to be immediately visible to any
applications running on NFS clients.Availability
This appears to be added for the RedHat/CentOS
5.4 release cycle and should be available in those or later releases.
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