The NearStore VTL provides the following advanced configuration features. Some of these features simply need to be enabled, while others require additional configuration after they are turned on. The preface to the task instructions for enabling advanced features provides a description of the feature, as well as a link to any further configuration that might be required.

The NearStore VTL advanced features follow:

Customer Accounts

You can use the NearStore VTL to create and manage multiple customer accounts. Each account has an administrator, who can manage the resources (virtual libraries and volumes) that you associate with the account.

This feature requires additional setup after you enable it. See the section called “Working with Customer Accounts” for more information.

Storage Pools

The NearStore VTL supports the use of storage pools, which are groups of disks that you can organize into specific storage resources. When you use storage pools with the NearStore VTL you can decide which virtual libraries use which disks. You do this by assigning your virtual libraries to storage pools when you create them.

Storage pools are useful for guaranteeing a separation of data (such as accounting and engineering) as well as enabling you to create high and low performance groupings of disk resources.

The NearStore VTL dynamically load balances across the available disks in order to achieve optimal performance. When using storage pools, the NearStore VTL load balances only across the disks in a specific storage pool.

The default behavior of the NearStore VTL is to group all disks into a single (called the default) storage pool.

This feature requires additional setup after you enable it. See Working with Storage Pools for more information.

Physical Tape Validation

When you enable the Physical Tape Validation option, the NearStore VTL stores a checksum for each physical tape that it imports. When a virtual tape that was created as the result of a physical tape import is exported, the NearStore VTL validates the stored checksum against the checksum of the physical tape to which it is being exported.

If the physical tape is the correct one, the export will continue. If it is not, the export will be paused and you will be prompted to load the correct physical tape into an available physical tape drive. This process helps to ensure that the wrong physical tape is not overwritten. Physical tape validation is the most useful when you are working with stand-alone tape drives.

This feature requires no additional configuration once you enable it.

Tape Pick List

Each time the NearStore VTL requires a tape that is not in the physical tape library, it will generate an action. This action requests that you load the physical tape, identified by a barcode, into an available physical tape drive or library.

When you enable the option to use physical tape picks lists, the NearStore VTL will also maintain a list of all physical tapes that need to be loaded into physical tape drives.

See the section called “Using Physical Tapes (Loading Physical Tape Drives)”.

Host Access Control

If you want to restrict access to virtual libraries on a host-by-host basis, you can enable the device access functionality of the system. This will enable you to map hosts to virtual libraries. This function is also called Host access control.

These mappings can be either dedicated or shared. When the mapping is dedicated there is a one-to-one mapping between the virtual library and a host. This means that only this host can access the virtual library.

When the mapping is shared, multiple hosts share access to a single virtual library. You can separate the access control for the medium changer and each virtual tape drive when using shared access.

If the system has multiple front-end ports, you can map individual virtual libraries to one or more ports. You can also break a virtual library into its components (virtual tape drives and robots) and map each virtual device to one or more ports.

See the section called “Working with Port Assignments” for more information.

Tape Set Addressing (HPUX)

Enable this feature if you are using an operating system that requires volume set addressing. For example, HP-UX requires volumes set address if it needs to see more than 8 LUNs. There is no further configuration required once you enable this feature. Note that Volume Set Addressing is a system-wide setting. If it is set, the NearStore VTL may no longer work correctly on hosts that do not support this mode of addressing.

Over allocation

Without over allocation, the NearStore VTL automatically reserves enough disk space for any virtual tapes that you create. For example, if you create a virtual tape with a 40GB capacity, the NearStore VTL will reserve 40GBs of space for the virtual tape.

Because the NearStore VTL performs dynamic load balancing, it does not actually allocate space on a particular disk(s). Rather, the NearStore VTL reserves space from either a user-defined or the default storage pool. This means that the NearStore VTL automatically reserves enough space for each virtual tape that you create. It also means that you must have enough space available for each virtual tape that you create.

If you would like to create virtual tapes, even when you don’t have enough available disk space, you should enable the NearStore VTL over allocation feature. When this feature is enabled, the NearStore VTL allocates disk space to virtual tapes as needed, regardless of how many volumes you initially create. This feature is sometimes called Capacity on Demand.

Tape optimization

Most physical tape drives compress data, but not all data is compressible at the same rate. This means that the amount of data that is written to tape will vary from backup to backup. This presents a challenge when trying to fill a virtual tape with enough data to fill most of a physical tape when a NearStore VTL exports the virtual tape. If, on the other hand, the virtual tape has too much data, you will not be able to export it.

When you use the tape optimization feature, the system monitors the compressibility of each data stream and dynamically adjusts the amount of data that it is writing to the virtual tape. This ensures that the virtual tapes will make the best use of physical tape when they are exported.

You enable tape optimization on a library-by-library basis. See the section called “Working with Virtual Libraries” for more information.

Tape Cloning

When you enable the tape cloning option for a specific virtual library, the NearStore VTL maintains a physical tape copy of each virtual tape that is associated with that virtual library. See the section called “Using Physical Tapes (Loading Physical Tape Drives)”.

The process by which this is accomplished is very similar to the one that the NearStore VTL uses to export data from a virtual tape to a physical tape. The main difference is that with cloning, the NearStore VTL does not delete the virtual tape once its data is copied to physical tape.

When you enable the Deferred Cloning option, you specify a span of time, during which the NearStore VTL will not create clones. Any changes that are made to the virtual tapes during this period of time will be held in queue until the deferred cloning time period has expired. At this point, these changes will be copied to the appropriate physical tapes.

When turned on, deferred cloning is applied to every virtual library in the system for which cloning is enabled. You cannot enable deferred cloning for only a specific virtual library.

Enabling Configuration Options

Complete the following to set advanced configuration options for the system:

Virtual libraries use virtual tape drives. Like virtual libraries, virtual tape drives are defined by type. The type of virtual tape drive used defines the capacity of the virtual tape that can be supported. The capacity of the virtual tape drive should match the native capacity of the physical tape drive to which you will be exporting data.

Because most physical tape drives compress data, you might want to enable the NearStore VTL tape optimization feature. When this feature is enabled, you can set the virtual tape drive type to support either LZS (STAC) or ALDC compression. See the section called “Using Physical Tapes (Loading Physical Tape Drives)”.

Default and Custom Virtual Tape Drive Types

The NearStore VTL comes with a number of default virtual tape drive types. These types can be used in virtual libraries. They can also be modified and used as the basis for custom virtual tape drive types.

Creating Virtual Tape Drive Types

Complete this task to create/edit virtual tape drive types: