HP CIFS File Locking Interoperation

6.4 WINDOWS AND UNIX CLIENT ACCESS – NFS

Mounted File System

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

CIFS/9000

File

NFS

Windows

UNIX

PC-NFS

CIFS/9000

Clients