The DST shadow volume is a virtual NCP (NetWare Core Protocol) volume that consists of a primary storage area and a secondary storage area. The primary and secondary areas use NSS volumes.
The primary volume is an NSS volume that is mounted on the OES 2 Linux server that is running DST. Shadow volumes are known by their primary volume name. Typically, the primary volume is on the higher-performance device.
When the primary volume has a state of , the volume ID that is assigned as its NCP volume ID represents the DST shadow volume pair of volumes. The secondary volume does not have a separate volume ID while it is in the shadow relationship.
The secondary volume is an NSS volume that is mounted on the OES 2 Linux server that is running DST. This volume is also referred to as the shadow path. The secondary volume is also referred to as the secondary file tree.
The secondary volume is typically a new volume. It should have a similar setup as the primary volume for key attributes settings, such as Salvage, Encryption, and Lookup Namespace. For guidelines and caveats about using NSS volume attributes with Dynamic Storage Technology, see Table 5-2, DST Support for NSS Volume Attributes.
IMPORTANT:If a secondary volume has existing files that reside only on it, its files can end up as folders when they are moved from primary to secondary. To avoid this problem, ensure that you have applied the latest patches for DST on your server.
For information, see Section 14.5, Files that initially reside only on the secondary volume can end up as directories on the primary volume.
For information about using remote secondary volumes in a shadow volume, see Section C.0, Technology Preview: Creating and Managing DST Shadow Volumes with Remote Secondary NSS Volumes.
The primary file tree and the secondary file tree have the same directory structure. A file can be located in either the primary file tree or the secondary file tree. The merged view presents these two file trees as a single file tree, as shown in Figure 1-1, User View of the File System Directory.
The NCP clients and management tools see a merged view of files on the DST shadow volume when they access the primary volume. In OES 2 SP3 Linux and later, Novell CIFS also provides a merged view for CIFS users that access CIFS shares on the primary volume.
If Novell Samba is used with DST shadow volumes, a SMB/CIFS user sees the merged view that is provided by the ShadowFS component of DST.
New directories are created in the primary file tree. A configurable global policy called Replicate Primary Tree to Shadow determines when the directory path is created in the secondary file tree:
At the time when the directory is created in the primary file tree
Only when files are moved based on policy enforcement
Performance is better when the branches are created only as needed. For information see Section 8.1, Replicating Branches of the Primary File Tree in the Secondary File Tree.
Global policies govern the behavior of DST, and apply to all shadow volumes on a given server. Before you configure shadow volumes on the server, ensure that you configure the global policies listed in Table 9-1.
Table 9-1 Global Policies
|
Global Policy Parameter |
For Information |
|---|---|
|
REPLICATE_PRIMARY_TREE_TO_SHADOW |
Section 8.1, Replicating Branches of the Primary File Tree in the Secondary File Tree |
|
SHIFT_MODIFIED_SHADOW_FILE SHIFT_ACCESSED_SHADOW_FILE SHIFT_DAYS_SINCE_LAST_ACCESS |
Section 8.2, Shifting Files from the Secondary File Tree to the Primary File Tree |
|
DUPLICATE_SHADOW_FILE_ACTION DUPLICATE_SHADOW_FILE_BROADCAST |
Shadow volume policies manage how files are distributed across the shadow volume’s primary and shadow areas. A Shadow Volume policy allows you to specify when the policy is enforced (one time, hourly, daily, weekly, and so on), which volumes the policy applies to, which direction files are moved (primary to shadow or shadow to primary), and which files are moved (file type, modify date, access date, size, and so on). Multiple policies can be applied to the same volumes and multiple policies can be scheduled to run concurrently.
For information about configuring global policies for DST, see Section 3.0, Installing Dynamic Storage Technology.
For information about creating or modifying Dynamic Storage Technology policies for shadow volumes, see Section 10.0, Creating and Managing Policies for Shadow Volumes.
You can generate an inventory of the files located on the two volumes by selecting the link next to the primary volume on the Dynamic Storage Technology Options page. This provides statistics broken out for both volumes and for each volume separately. For information, see Section 11.3, Viewing Statistics for the Shadow Volume
The Inventory page allows you to navigate through the statistics reports to determine a list of files to be moved between the two volumes (primary to secondary, or secondary to primary). For information, see Section 11.4, Using Inventory Detail Reports to Move, Copy, or Delete Files on the Shadow Volume.