HP CIFS Server 3.0i Administrator's Guide version A.02.03.03

Special Notes for HA HP CIFS Server
There are several areas of concern when implementing Samba in the MC/ServiceGuard HA
framework. These areas are described below:
• Client Applications
HA HP CIFS Server cannot guarantee that client applications with open files on a HP CIFS
Server share, or, applications launched from HP CIFS Server shares, will transparently
recover from a switchover. In these instances there may be cases where the application will
need to be restarted and the files reopened as a switchover is a logical shutdown and restart
of the HP CIFS Server.
• File Locks
File locks are not preserved during failover. File locks are lost and applications are not
advised about any lost file locks.
• Print Jobs
If a failover occurs when a print job is in process, the job may be printed twice or not at all,
depending on the job state at the time of the failover.
• Symbolic Links
If you have your Samba server configured with follow symlinks set to yes and wide links set
to yes, the defaults for these parameters, you should be cautious.
Symbolic links in the shared directory trees may point to files outside any shared directory.
If the symbolic links point to files that are not in logical shared volumes, then, after a failover
occurs, the symbolic link may point to a different file or no file. Keeping the targets of all
shared symbolic links synchronized with all MC/ServiceGuard nodes at all times could be
difficult in this situation.
Easier options would be to set wide links to no or to be sure that every file or directory that
you point to is on a logical shared volume.
• Security Files
An important security file is secrets.tdb. Machine account information is among the important
contents of this file. Since this file will be updated periodically (as defined in smb.conf by
machine password timeout, 604800 seconds by default), HP recommends that you locate
secrets.tdb on a shared logical volume. The location of the secrets.tdb file is defined by the
smb.conf parameter, private dir. For example, private dir =
/var/opt/samba/shared_vol_1/private will result in the file
/var/opt/samba/shared_vol_1/private/secrets.tdb.
User authentication is also dependent on several entries in different security files. Other
important security files are the user password file, smbpasswd and passdb.tdb. If you have
your Samba server configured with the "passdb backend = smbpasswd", for example,
then you have an smbpasswd file. By default, this file is located in the path
/var/opt/samba/private but the passdb backend parameter can be in two parts, the backend
name and a location string that has meaning only to that particular backend. For example,
passdb backend = tdbsam:/var/opt/samba/private/path1/passdb.tdb,
smbpasswd:/var/opt/samba/private/path2/smbpasswd will result in files
/var/opt/samba/private/path1/passdb.tdb and /var/opt/samba/private/path2/smbpasswd.
For both the machine account file and user password file, HP recommends that you store
the files in a common and secure directory on a shared logical volume.
• Username Mapping File
If you configure your Samba server to use a username mapping file, HP recommends that
you configure it to be located on a shared logical volume. This way, if changes are made,
all the nodes will always be up-to-date. The username mapping file location is defined in
174 Configuring HA HP CIFS