HP CIFS File Locking Interoperation

6.5 WINDOWS AND UNIX/NFS CLIENT ACCESS – Local

and NFS Mounted File Systems

The diagram above shows a Windows client and a UNIX/NFS client requesting concurrent

file access on the CIFS/9000 server. The key issue for this configuration is understanding

when the client platform locking schemes can or cannot interoperate.

A UNIX/NFS process is not aware of Windows Mandatory Share Mode (Open Mode) locking.

Therefore, a Windows client may lock a file with Mandatory Share Mode locks, but the

UNIX/ NFS process may concurrently open and read or write to the file, despite the Windows

client file locks. 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.

Remember: competitors 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 those same UNIX/NFS processes

CIFS/9000

File

NFS

Windows

UNIX/NFS PC-NFS

CIFS/9000

Clients