HP CIFS File Locking Interoperation

6.3 WINDOWS AND UNIX CLIENT ACCESS – Local File

System

The diagram above shows a Windows client and a UNIX client requesting concurrent file

access on the CIFS/9000 server to a local 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.

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

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

PC-NFS

CIFS/9000

Clients