Using Shadow Tapes

Using Shadow Tapes
	Chapter 4. Using Advanced Features

When you set the advanced option Enable Shadow Tapes (and then enable shadow tapes for the library containing the virtual tape), whenever a virtual tape is exported to a physical tape, the virtual tape is moved to the shadow tape pool. A tape in the shadow tape pool is invisible to the backup application, and is not listed as part of a virtual library, but is available for quick access if the physical tape is later imported, and is available for reading if the physical tape is stored offsite, or is otherwise unavailable. If a physical tape with matching shadow tape is imported, the NearStore VTL automatically makes the read-only shadow tape available immediately—before the physical tape itself could be read into the appliance, but you can also manually import a shadow tape back into a virtual library using the Import from Shadow Tape Pool screen, described in the following section.

Shadow tapes have a retention period. Once the retention period expires, the shadow tape is marked expired and the space can be used for current backup operation; however, if more the space is needed for a current back up operation than is free or marked expired, the NearStore VTL can delete a shadow tape and reclaim the space even if there is still time remaining in the retention period.

Importing a Shadow Tape

Although automatically imported when the matching physical tape is imported into the NearStore VTL, you can also manually import a shadow tape, perhaps because the physical tape is offsite.

Complete this task to import a shadow tape:

From the Daily Tasks menu, located on the left side of the screen, click the Virtual Tapes task category, and then select the Import from Shadow Tape Pool tab. The Import from Shadow Tape Pool screen appears.
If you are using storage pools (the advanced option Use Storage Pools is set), there is a drop-down menu Storage Pool at the top of the screen that controls whether the shadow tapes for all storage pools, or just a selected one, are listed. Select the desired storage pool.
From the drop-down menu Destination Library, select the library to which you want to import the shadow tape.
Decide if you want the imported tapes to be read-only, or writable. The default is read-only. Change this by unchecking the Import Read-only check box.

The screen displays the following information:

Files—lists the number of files on the shadow tape.

Tape Label—displays the label (virtual barcode) of the shadow tape.

Originating Library—provides the name of the virtual library from which the shadow tape originated.

Raw Capacity—gives the specified capacity of the drive.

Data Written—specifies the amount of uncompressed data that the NearStore VTL has written to the tape.

Disk Used—provides the amount of disk being used by the tape.

Disk Compression—indicates whether disk compression is used on the tape.

Tape Smart Sizing—lists whether the tape uses tape smart sizing. If the tape does, the field displays the tape optimization algorithm used. If it does not, the field displays DISABLED.

Time Remaining (Days HH:MM)—lists the remaining retention time for the tape. A shadow tape can be deleted by the NearStore VTL if the space is needed for current backup operations, even if there is still time remaining in the retention period.
Select the tape or tapes to import using the check box at the start of the row for the tapes, or select all listed tapes by selecting the check box at the top of the column.
Click Reset to clear all of the tape selections, or click Apply to import the selected tapes into the selected destination library.

Viewing the List of Shadow Tapes

The NearStore VTL provides a comprehensive list of shadow tapes on the Shadow Tape Pool screen. This list includes the files, label, originating virtual library, and other properties for each shadow tape.

From the Configuration Tasks menu, located on the left side of the screen, click the Virtual Tapes task category, and then select the Shadow Tape Pool tab. The Shadow Tape Pool screen appears. If the advanced option Use Storage Pools is set, there is a drop-down menu Storage Pool at the top of the screen that controls whether the shadow tapes for all storage pools, or just a selected one, are listed. The screen displays the following information:

Files—lists the number of files on the shadow tape.

Tape Label—displays the label (virtual barcode) of the shadow tape.

Originating Library—provides the name of the virtual library from which the shadow tape originated.

Raw Capacity—gives the specified capacity of the drive.

Data Written—specifies the amount of uncompressed data that the NearStore VTL has written to the tape.

Disk Used—provides the amount of disk being used by the tape.

Disk Compression—indicates whether disk compression is used on the tape.

Tape Smart Sizing—lists whether the tape uses tape smart sizing. If the tape does, the field displays the tape optimization algorithm used. If it does not, the field displays DISABLED.

Time Remaining (Days HH:MM)—lists the remaining retention time for the tape. A shadow tape can be deleted by the NearStore VTL if the space is needed for current backup operations, even if there is still time remaining in the retention period.


Identifying Physical Tapes that Need Mounting (Tape Pick List)		Working with Storage Pools