HP CIFS Server 3.0f Administrator's Guide verison A.02.03

• vfs objects
• idmap backend
Other Samba Configuration Issues
Translate Open-Mode Locks into HP-UX Advisory Locks
The HP CIFS Server A.02.* versions can translate open mode locks into HP-UX advisory locks. This functionality
prevents HP-UX processes from obtaining advisory locks on files with conflicting open mode locks from CIFS
clients. This also means CIFS clients cannot open files that have conflicting advisory locks from HP-UX
processes.
You must change the map share modes setting in smb.conf to yes to translate open mode locks to HP-UX
advisory locks. The default setting of map share modes is no.
Performance Tuning using Change Notify
This section describes performance tuning using the Change Notify feature and internationalization.
The Samba Server supports a new feature called Change Notify . Change Notify provides the ability for a
client to request notification from the server when changes occur to files or subdirectories below a directory
on a mapped file share. When a file or directory which is contained within the specified directory is modified,
the server notifies the client. The purpose of this feature is to keep the client screen display up-to-date in
Windows Explorer. The result: if a file you are looking at in Windows Explorer is changed while you are
looking at it, you will see the changes on the screen almost immediately.
The only way to implement this feature in Samba is to periodically scan through every file and subdirectory
below the directory in question and check for changes made since the last scan. This is a resource intensive
operation which has the potential to affect the performance of Samba as well as other applications running
on the system. Two major factors affect how resource intensive a scan is: the number of directories having
a Change Notify request on them, and the size of those directories. If you have many clients running Windows
Explorer (or other file browsers) or if you have directories on shares with a large number of files and/or
subdirectories, each scan cycle might be very CPU intensive.
To counteract the possible performance impact, you can control how often Samba scans for changes in the
directories it has been requested to monitor. The parameter that controls how often Samba scans for changes
is Change Notify Timeout. The parameter value represents the number of seconds between the start of each
scanning cycle. The default value is 60. So, if your system takes 55 seconds to complete the scan of all the
directories with Change Notify requests , it would be under a heavy load at nearly all times.You can increase
the Change Notify Timeout value to a larger number to decrease how often these Change Notify directory
scans are done. The trade off is that your clients will take longer to see that changes were made in the
directories that they have placed Change Notify requests on. You will have to decide what the right trade-off
is: performance loss or slow updates to client file browsers.
Special Concerns when Using HP CIFS Server on a Network File System (NFS) or a
Clustered File System (CFS)
Both NFS and CFS provide file system access to unique file storage from multiple systems. However, controlling
access to files, particularly files open for write access, from multiple systems poses challenges. Applications
are not necessarily network or cluster-aware. Applications may not be able to make use of locking mechanisms
when multiple systems are involved. You need to be aware of the following things when using HP CIFS Server
in either an NFS or a Veritas CFS environment:
• CIFS Server running simultaneously on multiple nodes should not use either NFS or Veritas CFS to
concurrently share the smb.conf configuration and its subordinate CIFS system files in
/var/opt/samba/locks and /var/opt/samba/private.
There are operational reasons why multiple nodes should not share a configuration file concurrently
such a name/IP registration conflicts, etc. Also, sharing ansmb.conf file will likely lead to sharing
CIFS Server system data, increasing the likelihood of concurrent file access and the possibility of CIFS
Server corruption.
• Beginning with version A.02.02, HP CIFS Server does not start if another master daemon is sharing
the daemon PID files including a daemon on another node. (By default, PID files are found in the
38 Installing and Configuring the HP CIFS Server