Because the NearStore VTL appliance operates in an environment that is specific to its function, some of the terms that are used in this guide do not necessarily follow the standard dictionary definition that you might expect. This section provides the NearStore VTL-specific definitions of these terms.

action

An action is an activity that requires manual intervention. When the NearStore VTL Appliance cannot proceed without manual intervention, an entry is created in the Action Required list. The action is usually part of the normal operation, e.g., loading a physical tape into a tape drive, but it may also be an exceptional condition, such as a tape drive that is not working correctly. The condition that caused the action must be resolved before the action required entry will be deleted.

administrator

The administrator account is the privileged account. Only the administrator can manage the system configuration. The administrator can perform such tasks as adding disks, physical tape devices and new users; managing the import/export tapes; setting the various system preferences and the like.

ageing policy

Ageing policies are set and managed by backup applications. The NearStore VTL does set or manage ageing policies (but see shadow tapes).

clone

Transfer of data from virtual tape to physical tape (occurs after unload of a changed tape). Key difference with export is that after the clone is done, the virtual tape stays in the virtual library.

customer

This is an optional feature that is enabled in the Configuration Tasks >Advanced >Options page. If the administrator chooses to use customers, then every virtual library belongs to a customer. An account is created that allows the customer to log in to NearStore VTL. The Customer can manage jukeboxes that belong to the customer.

delete (a virtual tape)

Deletes the virtual tape from the VTL (using menu Configuration Tasks -> Virtual Tapes -> Delete Virtual Tape). Virtual tapes are also deleted (blocks freed up on disk) after the completion of an Export.

eject

Moving of virtual tape to entry/exit port - this will start the export process.

events

Events are recorded in the Event log when an item of interest to the administrator occurs. An event may or may not have an associated Action Request.

export

Transfer of data from virtual tape to physical tape (occurs when you eject a virtual tape from the virtual library). After the export has been completed, the virtual tape is deleted from the VTL

export request

An export request is created when a virtual library exports a virtual tape. A virtual tape may be exported by sending a SCSI command to the virtual library (usually from a backup application) or by using the NearStore VTL web interface. The export request tracks the process of exporting the data from the virtual tape

import request

An import request can be created by either the administrator or a customer. A virtual tape can be imported by sending a SCSI command to the virtual library or by using the NearStore VTL web interface. The import request will track the process of importing the data from the physical tape.

NearStore VTL appliance

The NearStore VTL appliance refers to the NearStore VTL controller and all of the physical disks and physical tape drives used by the NearStore VTL controller.

pass through mode

When data is imported from a physical tape to a virtual tape, the data can be accessed shortly after the importing starts. This is invoked by moving the virtual tape into a virtual tape drive.

physical disk

Physical disks are connected to the NearStore VTL controller. All of the data stored in the virtual system is stored on the physical disks.

physical tape drive

Physical tape drives are connected to the NearStore VTL controller. They can be connected either through the Fibre Channel or through the parallel SCSI. The physical tape drives are used to transfer the data from the virtual tape to a physical tape. The data is read during import and written during export.

physical tape

A physical tape is a physical piece of tape media. It is called physical tape to clearly differentiate it from a virtual tape.

quick load

When the data on a physical tape is imported to a virtual tape using the quick-load option, only the first 1 MB of data is transferred. This is useful if the virtual tape will immediately be overwritten with new data. The first 1 MB allows the data management application to verify the virtual tape before it is overwritten. If an attempt is made to read or position beyond the 1 MB of data actually imported, then an I/O error is returned. The virtual tape may be reimported in a normal mode to permit access beyond the 1 MB.

RAID group

RAID groups are constructed from the NearStore VTL-attached physical disks, and provide a virtualization layer between the physical disks and the virtual tapes. This layer lets you add, remove and replace the physical disks without affecting the structure of the virtual tapes or the data stored on the tapes. If a physical disk in a RAID group fails, the disk can be replaced, and the data on the failed disk is reconstructed on to the new disk.

shadow tape

When a virtual tape is exported to a physical tape, the virtual tape is removed from the virtual library, but an option is available when a virtual library is created, to store virtual tapes in the shadow tape pool after a virtual tape is exported. A tape in the shadow tape pool is called a shadow tape.

The NearStore VTL manages the space used by shadow tapes, and can deleted a shadow tape if the space is needed for new backup data. An administrator can set a preferred retention time for shadow tapes; if space is needed, but the retention period has not expired, the NearStore VTL sends a notification before deleting the shadow tape.

smart sizing

When tape smart sizing is enabled, NearStore VTL estimates the rate at which the data being sent to it from a backup application can be compressed. This allows NearStore VTL to send an end of tape signal to the backup application only when the compressed size of the incoming data fills the tape.

storage pool

Storage pools are an optional feature of NearStore VTL that allow the administrator to partition a group of disks. When virtual libraries are assigned to a storage pool, the volumes created in the library are stored only on disks that belong to that storage pool.

tape operator

The tape operator is a special account with limited privileges. The tape operator is responsible for getting physical tapes, loading them into physical tape drives, and unloading the drives when the NearStore VTL appliance is finished with the tape.

tape optimization

see smart sizing

tape pick list

Tape pick lists are an optional feature of NearStore VTL. A tape pick list is a list of physical tapes required by NearStore VTL. It is used by the tape operator to get all of the tapes that NearStore VTL needs. NearStore VTL then recommends that the tapes are loaded into specific drives.

virtual library

A virtual library is a logical representation of a physical tape library. It exhibits all the behaviors of a physical tape library. It appears to have a robotic arm, one or more tape drives, tape cartridge slots, mailbox (entry/exit) slots, and a barcode reader. It responds on the bus in exactly the same way as a physical tape library.

virtual library type

A virtual library type determines how many slots, how many virtual tape drives, and what type of virtual tape drives are in a virtual library. NearStore VTL has several predefined virtual library types. The administrator can create additional virtual library types if required.

virtual tape

A virtual tape is a logical representation of a physical tape. Virtual tapes are used inside virtual libraries and written to by virtual tape drives in the same way as are physical tapes.

virtual tape drive

A virtual tape drive is a logical representation of a physical tape drive. Virtual tape drives are configured within virtual libraries. A virtual library can have one or more virtual tape drives. Each virtual tape drive emulates a standard tape drive.

virtual tape drive type

A virtual tape drive type determines how a virtual tape drive responds to SCSI inquiries and the capacity of the tapes written by the virtual tape drive. NearStore VTL has several predefined virtual tape drive types. The administrator can create additional tape drive types if required.