You can configure global policies for how files in the secondary file tree are automatically moved back to the primary volume. By default, files are moved back to the primary if they are modified, but not if they are accessed.
You can control how files are automatically moved from the secondary storage area to the primary storage area by configuring three parameters:
Shift Modified Shadow Files
Shift Accessed Shadow Files
Shift Days Since Last Access
IMPORTANT:If you use shadow volumes in a cluster, ensure that you set the same global policies on each OES 2015 SP1 node in the cluster.
This section describes the parameters, and recommends combinations of the policies to achieve different goals.
When files in the secondary file tree are modified, a configurable global policy called Shift Modified Shadow Files allows the files to be moved to the primary file tree (default), or kept in the secondary file tree. If a file is modified when this parameter is enabled, the file is automatically moved back to the primary storage area when the file is closed. This global policy applies to all DST shadow volumes on a given server. The policy does not move files that were modified prior to the setting being enabled.
Valid settings for Shift Modified Shadow Files are:
Disabled (0): When a file that resides on the secondary storage area is modified, it remains on the secondary storage area.
IMPORTANT:Applications are not aware that DST stores files in two locations. Depending on how an application works, a file might reside on the secondary storage when it is opened, and reside on the primary storage after it is modified.
For example, when you open a file to modify it, Microsoft Word creates a new temporary file and copies the content to it. It saves any changes in the new file, and deletes the old one. Because DST creates all new files on the primary location, the temporary file is created and saved on the primary storage, and the old file is deleted on the secondary location.
This behavior is not unique to Microsoft applications; other word processors and applications behave in the same fashion. When you plan your solution, you must be aware of how the applications you use actually work. If an application’s behavior overrides your intended data locations in the shadow volume, you can use policies to achieve the desired separation.
Enabled (1, default): If a file that resides on the secondary storage area is modified, it is automatically shifted to the primary storage area after it is closed. The file remains on the primary storage area until a policy is enforced that shifts it to the secondary storage area.
For example, if your policy is to place newer files in the primary file tree and to place older files in the secondary file tree, you want an older file in the secondary file tree to move to primary file tree if the file’s content is modified. The Shift Modified Shadow Files parameter is enabled by default, so this is the default behavior.
On the other hand, if you are placing files of one type (such as .doc and .ppt) in the primary area and files of a different type (such as.mp3 and .jpg) in the secondary area, you want files to stay where they are whenever they are modified. In this case, you should disable the Shift Modified Shadow Files parameter.
When files in the secondary file tree are accessed (but not changed), a configurable global policy called Shift Accessed Shadow Files allows the files to be left in the secondary file tree (default), or to be moved to the primary file tree. When this parameter is enabled, a file is shifted if it is accessed as read-only a second time during a specified period of time. The file is automatically moved back to the primary area when the file is closed. By default, the period of time is 1 day. Use the Shift Days Since Last Access parameter to specify the period of time. This global policy applies to all DST shadow volumes on a given server.
Valid settings for the Shift Accessed Shadow Files are:
Disabled (0, default): When a file that resides on the secondary storage area is accessed twice in the specified period, it remains on the secondary storage area.
Enabled (1): If a file that resides on the secondary storage area is accessed twice in the specified period, it is automatically shifted to the primary storage area after it is closed. The file remains on the primary storage area until a policy is enforced that shifts it to the secondary storage area.
For example, if you are placing files that are changing in the primary area and files that are not changing in the secondary area, you want files to stay where they are whenever they are accessed but not changed. The Shift Accessed Shadow Files parameter is disabled by default, so this is the default behavior.
On the other hand, if your policy is to place in-use files in the primary file tree and to place unused files in the secondary file tree, you want an in-use file in the secondary file tree to move to primary file tree if the file is accessed, whether it changes or not. In this case, you should enable the Shift Accessed Shadow Files parameter.
The Shift Days Since Last Access parameter specifies the number of days to use when determining if a file should be moved back to the primary storage area. When it is used with SHIFT_ACCESSED_SHADOW_FILES, the parameter sets the time when files are migrated back to the primary storage area after the second access within the specified elapsed time.
Valid settings for the Shift Accessed Shadow Files are:
Disabled (0): Files are not shifted on access.
Number of Days (1 to 365): If a file that resides on the secondary storage area is accessed twice in the specified period, it is automatically shifted to the primary storage area after it is closed. The default is 1 day.
Table 7-1 describes use cases for shifting files based on the global policies.
Table 7-1 Shift Behaviors for Files in the Secondary File Tree
|
Don’t Shift Modified Shadow File to Primary |
Shift Modified Shadow File to Primary (Default) |
|---|---|---|
|
Don’t Shift Accessed Shadow File to Primary (Default) |
Files can be modified or accessed without being shifted to the primary file tree. For example, you can separate files by file type, with the less important files in the secondary area. Thereafter, the files remain where you moved them. You can periodically apply volume-level policies that move file types from the primary to the secondary. Back up the primary area more frequently because it contains the most important file types. |
Modified files are shifted to the primary file tree, but accessed files are not. This is the default combination. Separate files so that recently modified files are located in the primary area. Older files remain in the secondary area. Back up the primary area more frequently because it contains all of the recently changed files. |
|
Shift Accessed Shadow File to Primary |
Files are shifted when they are accessed twice in a specified period, but not when they are modified. No use case exists for this combination. |
Files are shifted when they are modified, or if they are accessed twice in a specified period. This is desirable for migration-on-demand solutions that move data gradually from an old volume to a new, higher-performance location. Unchanged, seldom-used files are available to users, but do not require frequent backups. |
To configure the Shift Modified Shadow Files parameter:
Log in as the root user to OES Remote Manager.
Select Manage NCP Services > Manage Server to view the Server Parameter Information page.
Click the link for the SHIFT_MODIFIED_SHADOW_FILES setting.
In New Value, do one of the following:
Disable Modified Files from Shifting to Primary: Type 0 to keep files on the secondary storage area when they are modified.
Allow Modified Files to Shift to Primary: Type 1 to shift files on the secondary storage area to the primary storage area when they are modified. This is the default.
Click Change.
On the Server Parameter Information page, verify that the new setting is displayed for the SHIFT_MODIFIED_SHADOW_FILES parameter.
To configure the Shift Accessed Shadow Files parameter:
Log in as the root user to OES Remote Manager.
Select Manage NCP Services > Manage Server to view the Server Parameter Information page.
Click the link for the SHIFT_ACCESSED_SHADOW_FILES setting.
In New Value, do one of the following:
Disable Accessed Files from Shifting to Primary: Type 0 to keep files on the secondary storage area when they are accessed. This is the default.
Allow Accessed Files to Shift to Primary: Type 1 to shift files on the secondary storage area to the primary storage area when they are accessed twice during a specified period.
Click Change.
On the Server Parameter Information page, verify that the new setting is displayed for the SHIFT_ACCESSED_SHADOW_FILES parameter.
To configure the Shift Days Since Last Access parameter:
Log in as the root user to OES Remote Manager.
Select Manage NCP Services > Manage Server to view the Server Parameter Information page.
Click the link for the SHIFT_DAYS_SINCE_LAST_ACCESS setting.
In New Value, do one of the following:
Disable: Type 0 to disable this parameter.
Number of Days: Type an integer value from 1 to 365 (in days) that specifies the number of days to wait for a second access of a shadow file. If the second access occurs during this period, the file can be moved if the SHIFT_ACCESSED_SHADOW_FILES parameter is also enabled.
Click Change.
On the Server Parameter Information page, verify that the new setting is displayed for the SHIFT_DAYS_SINCE_LAST_ACCESS parameter.
For information about using the SET command to modify these global policies, see Section A.4, Configuring Global DST Policies by Using the SET Command.