Client-Side Caching for Offline Files

With the putback of PSARC 2008/758, the CIFS service provides per-share configuration options to support client-side caching (csc) for offline files, which can be set using sharemgr or zfs.  Note that client-side caching and offline files are managed entirely by clients, and the options discussed here provide per-share policy advice to clients.  The csc options are shown in below.

• manual
  Clients are allowed to cache files from the specified share for offline use as requested by users but automatic file-by-file reintegration is not allowed.  This is the default setting.
  
  
• auto
  Clients are allowed to automatically cache files from the specified share for offline use and file-by-file reintegration is allowed.
  
  

• disabled
  Client-side caching is disabled for this share.

First, we need to create a file system and share it.  For use with SMB/CIFS, it's best to create a mixed-mode zfs file system.  If you have both NFS and SMB clients using a mixture of different character sets on the same file system you may also want to set utf8only and consider the charset=<access-list> NFS share property that Doug described in a recent blog entry.

        zfs create -o casesensitivity=mixed -o utf8only=on tank/zvol
        zfs sharesmb=name=zvol tank/zvol

        sharemgr show -vp
        default nfs=()
        zfs
            zfs/tank/zvol smb=()
                zvol=/tank/zvol

The default, when no specific csc option has been set, is equivalent to csc=manual.

Since this share is a member of the zfs group, share options such as client-side caching must be set using the zfs command.  In the following example the csc option is set to auto.

        zfs sharesmb=name=zvol,csc=auto tank/zvol

        sharemgr show -vp
        default nfs=()
        zfs
            zfs/tank/zvol          smb=(csc="auto")
                zvol=/tank/zvol

Note: The zfs command interprets sharesmb as a property with a single value, even though that value may contain a list of share properties.  When using the zfs command to set share options, all desired share options must be set each time the property is set or modified - as illustrated above.  Failure to do this may result in share properties being unset.  For example, after the two commands below, the share name would be tank_zvol rather than zvol.

zfs sharesmb=name=zvol tank/zvol
zfs sharesmb=csc=auto tank/zvol <-- resets the share name to tank_zvol

Alternatively, we can use sharemgr's default group or create our own group.  In this example, we add a share to zgroup and disable client-side caching for that share.

        sharemgr create -P smb zgroup
        sharemgr add-share -r zvol2 -s /tank/zvol2 zgroup
        sharemgr set -P smb -p csc=disabled -r zvol2 zgroup

        sharemgr show -vp
        default nfs=()
        zfs
            zfs/tank/zvol          smb=(csc="auto")
                zvol=/tank/zvol
        zgroup smb=()
            /tank/zvol2
                zvol2=/tank/zvol2  smb=(csc="disabled")

Note that, as illustrated above, the csc setting is per-share.

The csc options are also valid for autohome shares in the smbautohome map.  As with zfs sharesmb, multiple options can be specified as a comma separated list.  For example,

        *      /export/home/&   csc=disabled,description=&
        john   /export/home/&   csc=auto,dn=sun,dn=com,ou=users

Some useful links for managing offline files on Windows:

• How to use offline files in Windows XP
  http://support.microsoft.com/kb/307853
  
  
• The Cache Option for Offline Files Must Be Disabled on Roaming User Profile Shares
  http://support.microsoft.com/kb/287566
  
  
• How to re-initialize the offline files cache and database
  http://support.microsoft.com/kb/230738
  
  
  

Posted at 07:10PM Jan 09, 2009 by Alan Wright in Sun  |  Comments[2]