1. Administrator's Guide
  2. Logical Library Support
  3. Creating a Logical Library

Creating a Logical Library

Before you use the ACSLS GUI or lib_cmd to create a logical library, a physical library must have been created using the acsss_config or config acs utility. An audit should also be performed before you create the logical library.

When creating a logical library, you:

  • Specify a physical ACS

  • Specify the attributes of the logical library

  • Assign one or more physical drives

  • Assign one or more physical volumes

  • Specify client access to the logical library

Specifying a Physical ACS

When you specify the backing ACS for a logical library, you automatically limit the drives and volumes that can be assigned to the logical library in subsequent steps. Only those drives and volumes that are in that ACS, and are not already assigned to another logical library, are available.

A logical ACS number is assigned by ACSLS when the logical library is created. The ACS number range for a logical library is n001-n999 where n = (1 + the backing physical ACS ID).

For example:

  • a logical library backed by physical ACS 0 might be 1001

  • a logical library backed by ACS 4 might be 5001

Specifying the Attributes of the Logical Library

The following attributes can be specified for a logical library:

  • Unique name for the logical library

  • Capacity

    This is the maximum number of volumes that can be accessible in the logical library at any time (the number of storage elements that they would be able to inventory). The minimum is 0, and the maximum is 64,536. There is no default.

    The capacity can be used both to restrict the size of a logical library (setting a limit that is less than the actual physical capacity) or to over-allocate physical capacity (setting a limit higher than what is actually available).

    • Number of import/export cells

      The minimum is 2, and the maximum is 400. The default value is 2.

    • Number of drive slots

      This is the maximum number of drives that can be assigned. The minimum is 0, and the maximum 500. There is no default.

    • Label format

      Today, support for longer volume labels in physical libraries relies on library firmware and configuration.

      However, logical libraries can report the entire barcode (the 6 volser characters with the media domain and type suffixed). This provides an 8-character volser: xxxxxxL4. The logical library is configurable so the media domain and type can either be appended to the volser or they can prefix the volser (such as, L4xxxxxx).

      The label formats supported, are: 6-character, 8-character-suffix (the default), and 8-character-prefix.

Assigning One or More Physical Drives

Any physical drive that is installed and configured in the backing ACS can be added to a logical library. There are no restrictions on drive type for a logical library.

Physical drives that are allocated to logical libraries:

  • become inaccessible to ACSAPI clients.

    The physical libraries, along with any drives and volumes that are not allocated to logical libraries, remain accessible to ACSAPI clients.

  • are allocated exclusively.

    They cannot be shared across logical libraries.

You cannot assign more physical drives to a logical library than the number of drive slots that were specified when creating the logical library. However, it is possible to assign fewer drives since a logical library can have empty drive slots.

Note:

Locked drives cannot be assigned to a logical library. (A locked drive is already being used by some ACSAPI client.)

You can increase or decrease the number of drive slots at any time. If you want to lower the number of slots to a value below the number of currently-assigned physical drives, you first have to un-assign some drives.

Assigning One or More Physical Volumes

When creating a logical library, you specify its capacity: the maximum number of volumes that can be accessible at any given time. Make volumes accessible by assigning them to a logical library.

Assignment is exclusive - a cartridge can only be assigned to one library. Most cartridges that are present in the backing ACS, and that have not already been assigned to any logical library, are eligible for assignment.

You can not assign volumes that are:

  • cleaning cartridges (ACSLS and the library handle cleaning).

  • locked (A lock indicates use by an ACSAPI client).

  • owned (An owner indicates use by an ACSAPI client).

Once the number of accessible volumes in a logical library has reached the maximum capacity, no more cartridges can be added. Either increase the library capacity, or free some used space.

Space is released in a logical library when an assigned volume becomes inaccessible. This can happen when an assigned volume is:

  • marked for eject by FC client.

  • ejected from the library.

  • marked absent by ACSLS.

Volumes that are assigned, but inaccessible, are automatically reactivated if they become accessible again (for example, an ejected volume can be re-entered into the backing ACS) and if the logical library has space available.

Finally, you can free space in a logical library by un-assigning volumes. A cartridge can be unassigned from a logical library if the cartridge is not in use (such as, it cannot be mounted in a logical drive, it cannot be selected for an eject operation, and so forth).

Notes:

  • Un-assigning a volume from a logical library does not imply any type of deletion or eject operation. Ejecting a volume does not imply an un-assign operation.

  • Remember that physical storage cells are neither pre-allocated, nor assigned to a logical library. A logical library contains specific volumes rather than specific cells. Cells only “belong" to a logical library when they contain an assigned volume.

  • The total number of accessible volumes among logical libraries that share a backing ACS can never be more than the physical capacity of the backing ACS.

The number of volumes assigned to a logical library can be displayed from lib_cmd or from the Logical Library Detail Information page in the GUI. Assigned volumes are shown as two separate counts:

  • Accessible Volumes - This represents volumes that are assigned, are in the library, and are generally available for client use.

  • Inaccessible Volumes - This number represents volumes that are assigned, but are not available for client use due to any of the following reasons: 1) the volumes have been marked as absent or ejected; 2) the volumes have been marked for eject by the FC client; 3) the volumes have been re-entered but the logical library was full; 4) the volumes have been re-entered into the wrong physical library.

You can increase or decrease the number of storage slots at any time. If you want to lower the number of slots to a value below the number of currently-assigned physical volumes, you first have to un-assign some volumes.

Specifying Client Connections

The ACSLS SCSI Media Changer Interface makes logical libraries available for client use over a Fibre Channel (FC) connection. To allow FC clients to access the logical libraries, you will need at least one FC port that is configured to operate in target mode.

If you configured a target port while running install.sh during the ACSLS installation process, continue to create the logical library. If you have not yet configured a target port, use getHba.sh to configure the target port. Then, shutdown ACSLS and reboot the ACSLS server. For more information, see How to Configure an FC Port in Target Mode.

Once you have configured a target port, the GUI makes it easy to manage client connections when you are creating or updating a logical library. The GUI screens provide a list of the target ports that are available on the ACSLS system, and also provide a list of any clients that have inquired about those ports over a FC connection. ACSLS automatically detects those inquiries and remembers the WWN of each client.

To assign a logical library to a client, check the appropriate boxes in the GUI.

Once you have configured a target port, it is easy to manage client connections either from lib_cmd or the GUI when you are creating or updating a logical library. Both the GUI and the interactive-mode lib_cmd provide a list of the target ports that are available on the ACSLS system. They also provide a list of any clients that have inquired about those ports over a FC connection. ACSLS automatically detects those inquiries and remembers the WWN of each client.

To assign a logical library to a client, use create mapping in lib_cmd or check the appropriate boxes on the Manage Connections page in the GUI.

A friendly 'alias' name can be used in lieu of the WWN to identify each client system. To assign an alias, use edit initiator in lib_cmd, or select the 'Edit Initiator Alias' operation on the Manage Connections page of the GUI

Fast Load

The ACSLS Fast Load setting controls how completion of the move command is reported when the destination element is a tape drive.

With Fast Load enabled, a success status is returned once the operation has been validated and accepted by ACSLS, but before cartridge movement begins. If some error should occur during movement, ACSLS does not report that information. The client is responsible for identifying when the volume has been loaded and is usable, and for timing out the request in the case of any error.

With Fast Load disabled (the default setting), success status is not returned until the physical library has reported that the movement is complete. However, if an error should occur during movement, ACSLS reports that information to the client.

Physical libraries may provide their own Fast Load option which can affect the time required before ACSLS would return a success status (but only when ACSLS Fast Load is disabled). When ACSLS Fast Load is enabled, the library setting would have no effect on client notification.