6.4WINDOWS AND UNIX CLIENT ACCESS – NFS Mounted File System
Clients
Windows | UNIX | CIFS/9000 | Windows |
CIFS/9000 | NFS |
File |
The diagram above shows a Windows client and a UNIX client requesting concurrent file access on the CIFS/9000 server to a NFS mounted file system. The key issue for this configuration is understanding when the client platform locking schemes can or cannot interoperate.
A UNIX process is not aware of Windows Mandatory Share Mode (Open Mode) locking, regardless of the NFS mount. A Windows client may lock a file on the CIFS/9000 server (in this case the server is also an NFS client) with Mandatory Share Mode locks, but the lock is not propagated over the NFS mount. CIFS/9000 has been enhanced to translate
Windows Mandatory Share Mode locks into byte range locks, thus providing locking interoperation with the UNIX advisory locking protocol and reducing the risk of data corruption. Windows applications expect mandatory share mode locking to be enabled, so share mode locking should remain enabled.
Remember: competitors that claim their Mandatory Share Mode locking interoperability mechanism provides comprehensive protection from UNIX/NFS concurrent file access, even if they do not participate in the advisory locking protocol. However, if a UNIX/NFS application is not properly coded to lock files, then there is no way to protect other UNIX/NFS processes from concurrent file access data corruption. If data can be corrupted by UNIX/NFS concurrent file access, then providing Windows Share Mode (open mode) locking protection from
22
