Media Management in a Silo

Because more than one software application can use a silo, media management in a silo requires extra operations to protect the volumes used by other programs from being overwritten by Backup.

The tasks described in this section deal with how volumes are specified for Backup to use, how volumes are mounted in the devices, and how volumes are identified and counted in the silo.

What Slot Numbers Mean in a Silo

In an autochanger, Backup specifies many of the functions by a slot number; silos use this same idea. In an autochanger, there is a fixed number of slots; Backup uses the slot number to refer to the physical location of a volume. However, a silo has a variable number of slots, starting at zero when you first configure it and limited by the silo license you purchased. The fundamental identifier of a silo volume is its barcode, which is often called a "volser" in silo documentation. The volser never changes over the life of a particular volume.

When the nsrjb command displays a list of the contents of a silo, it also displays a slot number. You can use the slot number to specify which volumes to mount, unmount, label, and inventory. Volumes are not always assigned the same slot number in the silo. The slot numbers in the silo are assigned dynamically, based on the sorted order of the barcodes that have been allocated. If you allocate more barcodes that fall earlier in the sort sequence, the slot numbers of all the volumes later in the sequence change.

Because the slot number is not a perfect identifier for silo volume, operations that might change the slot number cannot accept a slot number as arguments. For example, you cannot deallocate volumes based on slot numbers, because this operation can change the slot numbers of volumes being deallocated.

Using the CAP to Deposit and Withdraw Volumes in a Silo

A Cartridge Access Port (CAP) enables you to deposit and withdraw volumes in a silo without opening the door to the silo. The CAP is useful because you can add (deposit) and remove (withdraw) volumes in a silo without having to reinventory the entire silo. When you use the CAP to add or remove volumes, Backup does not automatically take inventory, read barcode labels, or locate empty slots in the silo. Use the silo inventory feature and Jukeboxes resource for these tasks.

You can use Backup commands or the silo management software to control the CAP on the currently supported silos to deposit and withdraw volumes in a silo. It is often more efficient to use the silo management software, especially to deposit or withdraw a large number of volumes.

The Backup command to allocate and deposit volumes is: The Backup command to deallocate and withdraw volumes is:

# nsrjb -a -Txxxx -d 

# nsrjb -x -Txxxx -w 

The deposit and withdraw functions are not available in the Backup administration program GUI.

On some silos (IBM 3494 and StorageTek silos when the CAP is set to automatic mode), the silo management software inserts volumes automatically. You cannot use Backup to insert volumes.

On StorageTek silos, due to differences between the internal operations of Backup and the StorageTek silo management software, Backup can only withdraw one volume at a time. You must physically remove the volume from the silo's CAP before you can withdraw any more volumes. On EMASS/Grau silos, Backup can control both the deposit and withdraw functions.

How to Allocate Volumes in a Silo

When you allocate volumes, you tell Backup which volumes it can use. Because more than one software application can use a silo, it is possible that a different application could read or write to volumes that belong to Backup. To prevent this problem, most silo management programs include methods of limiting access to volumes based on the hostname of the machine on which Backup and the other programs run. Backup does not provide any method for setting up this sort of protection; it must be configured by the silo management program.

When you allocate a volume, Backup queries the silo management software to verify that the volume you requested exists. If the volume exists, the volume is allocated to Backup. If the volume does not exist, the following message is displayed:

barcode xxxxxx is not present in the silo and was not added 

If you are allocating a range of volumes, the allocation continues after displaying the message. The message is informational and does not indicate a Backup error.

To allocate a silo volume, use either:

• The Add Library Volumes dialog box in the Backup administration program. Refer to the online help for instructions.

• The nsrjb -a -T barcode command. Refer to the nsrjb man page for further information on this nsrjb command, and refer to the stli man page for the proper format of barcode templates. You can use only a single barcode identifier or template after the -T option, but you can use the -T option more than once with the same nsrjb command.

To deposit volumes into a silo and then allocate them (on silos that require manual depositing, such as EMASS/Grau), place the volumes in the insert area, then issue the following command:

# nsrjb -a -Txxxx -d

On StorageTek and IBM silos, the silo management software deposits volumes automatically.

Mounting and Unmounting Volumes in a Silo

You must mount a volume before you read or write data on it. Volumes are mounted in a device in the silo by the robotic mechanism.

To mount a volume in a silo device, you can use either the Backup administration program or the nsrjb -l command. When you mount a volume, you must specify the volume, slot, or barcode.

You must dismount a volume before you can inventory the volumes in a silo or deallocate the volume from a Backup silo. To unmount a volume, you can use either the Backup administration program or the nsrjb -u command.

To specify a barcode identifier or template for the volumes, you can use the -T option with either nsrjb command.

Labeling Volumes in a Silo

Labels tell Backup the pool to which the volume belongs and what type of data the volume should contain. (For more information on volume labels, see "Labeling Storage Volumes ".) Backup cannot write data to a volume until you label the volume.

To label a volume in a silo, use either the Backup administration program or the nsrjb -L command.

Backup labels for volumes in a silo include both a regular Backup volume label (written on the media of the volume) and a silo barcode identifier. The volume label is usually based on the volume pool's label template. The barcode identifier is written on a physical label on the outside of the volume, which the barcode reader in the silo can scan during inventory.

By default, the use of barcodes and matching barcode labels and Backup volume labels are both enabled for a silo. You can change the Match Barcode Labels attribute, but do not set the Barcode Reader attribute to No. When you set the Match Barcode Labels attribute and the Barcode Reader attribute to Yes, the internal volume label Backup writes on the media of each volume matches the barcode label on the outside of the volume. When the labels match, it is easier to track volumes, but Backup does not require the internal and external labels to match.

With most silo management software, you can use unlabeled volumes. The management software assigns a "virtual" barcode label to those volumes. Although you can use volumes without barcodes, it is very difficult to maintain integrity. This is because after you remove the volume from the silo, the information about the virtual barcode is lost. You can reinsert any volume without a barcode into the silo under a virtual barcode that Backup (or another application) associates with some of your data.

Deallocating Volumes in a Silo

If you no longer need a volume in a silo for Backup, you can deallocate the volume. Deallocation is basically the same operation as removing a volume from an autochanger. Although the robotic mechanism cannot load the volume, the entries in the Backup media database remain intact. If you allocate the volume again later, Backup can retrieve the data from it.

Use deallocation when your silo license limits the number of slots you can use or when you move data offsite for safer storage. In the case where the license limits the number of slots, you might be able to leave the volumes in the silo, so you can easily reallocate the volumes when you need to access the data on them.

The allocation operation is not automatic. You must manually allocate the volumes again and reinventory them to let Backup access the data. In the case of removing the volume from the silo for off-site storage, you can either deallocate it with Backup and then use the silo management software to eject it from the silo, or you can perform both operations at the same time from the command line with the nsrjb -x -Txxxx -w command.

STK silos currently can only eject one volume at a time. The silo operator must remove each volume before another nsrjb -x -w command can be issued. If you deallocate and withdraw multiple volumes, they are all deallocated, but only the first is ejected. This limitation does not exist on EMASS/Grau or IBM 3494 silos.

How to Deallocate a Silo Volume

1. Unmount the volume from the device.

2. Use either the Backup administration program or the nsrjb -x -T barcode command to deallocate the volume.

   Refer to the online help for information about how to deallocate a silo volume using the Backup administration program. Refer to the nsrjb man page for further information on the nsrjb command. Refer to the stli man page for the correct format of barcode templates.

Taking a Silo Inventory

Take inventory of the volumes in a silo to make sure that the mapping between slot number and volume name is correct or to reconcile the volumes in a silo with the list of volumes in the Backup media database.

The slot number of a silo volume is not a numbered slot inside the silo, as it is in an autochanger. The slot number of a silo volume is the number of the volume's position in the list of volumes in a silo. You can view the slot number for each silo volume in the Backup administration program in the Jukebox Mounting dialog box.

Use the Backup administration program or enter the nsrjb-I command to inventory a silo. Backup examines all the volumes in the silo and compares the new list of volumes to the Backup media database. Then Backup produces a message listing any volumes located in the silo but not in the media database.

When Backup inventories a silo, the silo's barcode label reader reads the barcode labels on the outside of each volume. When a barcode matches an entry in the Backup media database, Backup does not need to load the volume into the device and read, and the inventory proceeds very rapidly. However, if Backup reads a barcode that does not match any of the entries in the media database, the volume must be mounted and read for a proper inventory.

You can inventory a range of slots or barcode labels if you are pressed for time and do not want to inventory all the volumes in your silo.