I don't want to make a specific statement regarding corruption
but I can explain how nbmand works and let you decide on what
to do.

The locking facility exists centrally within the OS and all
access (local, NFS or SMB) always goes through it regardless
of whether it is on or off.  The only difference is mandatory
versus advisory enforcement.  The behavior is:

System-wide coordination (nbmand on)
- Mandatory coordination across SMB, NFS, and local processes
- SMB open, rename, and delete synchronized with system-wide
  nbmand locks

No system-wide coordination (nbmand off)
- nbmand locks still taken for all access and processed as
  advisory reservations
- SMB service enforces mandatory locking internally

Note that SMB always enforces mandatory locking internally
regardless of the nbmand setting.

In real terms, because many operating systems do not provide
something similar to nbmand=on, many applications that operate
over both NFS and SMB have their own, private mechanism for
ensuring serialization.  If you know what applications are in
use, it will help you in making an informed decision.

On the question of home directories, all I can say is that we
operate home directories here on Solaris with a dataset per
user shared over both NFS and SMB, and we make extensive use
of automount maps.  We don't enable nbmand on those datasets
and I am not aware of anyone ever encountering a problem.


On 12/2/10 5:52 AM, Ryan John wrote:

Thanks for a great product, it really works well.

The following is not a CIFS problem, only background.

For some time now, we’ve been running into problems with shares that are
exported via CIFS and NFSv4

My Solaris systems are running snv_134 and the Linux systems are RedHat 5.5

We’ve isolated the problem to a known Linux bug:

We’ve patched our Linux kernels to try and cope, but we are still
running into occasional problems, that I can fix by turning off nbmand.

My question is, what are the implications of turning off nbmand locks on
a user’s home directory?

For example:

Can it lead to file corruption?

Are they there, only so that 2 users at the same time can’t write to the

If it’s to block multiple users accessing the file, is it safe in a home
directory only accessible to one user?


John Ryan
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