HP CIFS File Locking Interoperation

8.1 Network Appliance

Network Appliance markets very specific NAS servers that they call “Filers”. Filers are

single-purpose front-end “thin servers” used exclusively for storage access. NetApps employs

a feature called the “SecureShare” cross-protocol Lock Manager. NetApps literature claims

that SecureShare provides comprehensive multi-platform (heterogeneous) file locking

capability.

NetApps servers are single-purpose file servers running a proprietary OS called Data Ontap.

UNIX users and applications do not run on the system. Therefore, UNIX-Windows

concurrent file access is not an issue, and NetApps literature ignores UNIX file sharing

issues - probably for this reason. SecureShare does offer an interoperability mechanism for

Windows and NFS clients. SecureShare can protect Windows clients with Mandatory Share

Mode (open mode) locks from concurrent file access UNIX/NFS applications, 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 SecureShare cannot protect other UNIX/NFS processes from

concurrent file access data corruption. If SecureShare allows data to be corrupted by

UNIX/NFS concurrent file access, then providing Windows Share Mode (open mode) locking

protection from those same UNIX/NFS processes has limited value

Based upon Network Appliance documentation, SecureShare provides the following file

locking ability:

Mandatory Share Mode (Open Mode)

Network Appliance

Lock Windows Yes

Lock UNIX – no advisory locking Not Applicable

Lock UNIX – advisory locking Not Applicable

Lock UNIX/NFS – no advisory locking Yes

Lock UNIX/NFS – advisory locking Yes

Lock PC-NFS Yes

Byte Range Locking

Lock Windows Yes

Lock UNIX – no advisory locking Not Applicable

Lock UNIX – advisory locking Not Applicable

Lock UNIX/NFS – no advisory locking Yes

Lock UNIX/NFS – advisory locking Yes

Lock PC-NFS Yes

Oplocks

Break Oplock for Windows access Yes

Break Oplock for UNIX access – no

advisory

Not Applicable

Break Oplock for UNIX access - advisory Not Applicable

Break Oplock for UNIX/NFS – no advisory Yes

Break Oplock for UNIX/NFS – advisory Yes

Break Oplock for PC-NFS Yes

See Appendix B.5