| Working with Physical Tape Devices | ||
|---|---|---|
 |
Chapter 2. Configuring a NearStore VTL Appliance | 
|
| Working with Physical Tape Devices | ||
|---|---|---|
|
|
Chapter 2. Configuring a NearStore VTL Appliance |
|
Because copying data to physical tape for offsite storage is a part of most backup schemas, you will most likely want to export your virtual tapes to physical tape. You might also want to import data from a physical tape. To make this process as simple as possible, the NearStore VTL provides full support for most of the physical tape libraries.
Virtual and Physical Tape Libraries
A good way to understand the relationship between virtual and physical libraries is to look at the relationship between virtual tapes and physical tapes. Both of the virtual tapes and physical tapes that NearStore VTL creates are in the native format of the backup application. There is also a one-to-one correlation between virtual tapes and physical tapes. This means that for each virtual tape, there is a corresponding physical tape that has the same capacity and barcode.
This means that virtual and physical libraries must both use drives that are of the same type and capacity in order to be compatible with each other. This is important because you cannot export virtual tapes or import physical tapes if the drives are not compatible.
See the following for more information on virtual tapes and virtual tape drives:
Most physical tape drives compress the data that they write to tape. But because not all data is compressible at the same ratio, the actual amount of data that a drive writes to tape varies from backup to backup. Because you need to be able to export virtual tapes to physical tape, it is important that the data on the virtual tapes fits on the corresponding physical tapes. If it does not, the NearStore VTL cannot copy it to physical tape.
You can address this issue by making the capacity of the virtual tapes match the native capacity of the corresponding physical tapes. This however, does not make the best use of the physical tapes. For example, if your physical tape drive compresses data at a 2:1 ratio, you are using only around half the capacity of your physical tapes when you export virtual tapes.
The NearStore VTL offers a tape optimization feature that when enabled, samples the data that your backup application is sending to see at which ratio it can be compressed. This enables the NearStore VTL to dynamically adjust the size of the virtual tape to match the compressed capacity of the physical tape. This results in significantly better tape usage when you export the virtual tape.
The tape optimization feature is tuned for specific types of physical tape drives. The NearStore VTL comes preconfigured with configuration estimation algorithms set for each virtual tape drive type. You can use these default settings, or you can either update the drive type to use a new tape optimization algorithm or create a new virtual type.
See the following for more information on virtual library and drive types:
By default, NearStore VTL deletes a virtual tape after it successfully exports its data to the corresponding physical tape.
If you want NearStore VTL to maintain both physical and virtual copies of the volumes in a virtual library, you can enable the cloning feature for the virtual library.
Once you enable the cloning feature for a virtual library, the NearStore VTL copies the data from a virtual tape to its corresponding physical tape each time that the backup application sends data to the virtual tape and the virtual tape is ejected from the virtual tape drive.
Although the NearStore VTL maintains both virtual and physical copies of a volume, the backup application sees only the virtual tape.
When you no longer wish to keep both virtual and physical copies of the volume, you can simply export the virtual tape to physical tape.
Because there might be times during which you do not want to clone (your backup window for example), you can specify a span of time during which the NearStore VTL does not clone. This is an advanced option that you can enable from Configuration Tasks>Advance >Options. Select Enable Differed Cloning and set the times during which you do not want the NearStore VTL to clone.
See Advanced Configuration for more information.
Although the tasks in this section are written for physical tape libraries, they also work for stand-alone tape drives. Task that apply only to physical tape libraries are marked as such. Furthermore, areas in which the tasks differ for a stand-alone device are so noted.
Tasks for this subsection include:
Related tasks that are not in this section include:
The NearStore VTL displays all the physical tape devices that you have added to its configuration on the Physical Tape Device List screen. Each device is listed by its name. The NearStore VTL gives information about the device path, LUN, model, device, loader type, and status.
If the device is a part of a physical tape library, the Loader Type field displays changer. If the device is stand alone, the loader type is manual.
In the case of a library, the media changer itself is not displayed as a device.
Viewing the Inventory for an Attached Physical Tape Library
You can also use the NearStore VTL to scan or display the inventory of an attached physical tape library.
Complete this task to view the inventory of an attached physical tape library:
From the Configuration Tasks menu, located on the left side of the screen, click the Physical Tape Devices task category.
The Physical Tape Device List screen appears, and the NearStore VTL displays the following for each physical tape device that has been added to its configuration.
Nickname—gives the nickname of the physical tape device.
Port Name—provides the name port name information for each attached SCSI/Fibre Channel device. The port name is the port on the VTL appliance.
Serial Number—gives the serial number of the device.
Model—provides model information for the physical tape device.
Loader Type—specifies whether the device is either stand alone or part of a library. Stand-alone devices are specified as manual and libraries as changer.
Status—gives the status of the device. The device can be either online (enabled) or offline (disabled). If the device is online, the backup application can access it. If the device is offline, the backup application cannot access it.
Viewing the Physical Tape Library Inventory
Because the NearStore VTL is compatible with the barcode support provided by most physical tape libraries, you can use it to scan or display the inventory of attached physical tape libraries. The information provided by a scan includes the number of slots and drives in the physical tape library as well as the barcodes of any physical tapes.
Complete this task to view the inventory of an attached physical tape library:
Click changer from the Loader Type field of a physical tape device to view the inventory of the physical tape library with which it is associated.
The Changer Inventory screen appears and the NearStore VTL displays the following:
Number of Slots—specifies the number of slots in the physical tape library.
Number of Drives—gives the number of physical tape drives in the physical tape library.
Changer—provides the name of the media changer in the physical tape library.
Barcode—gives a list of the barcodes of the physical tapes that are currently in the physical tape library.
You can click Rescan to scan the inventory of the physical tape library.
When you add a physical tape library to the NearStore VTL appliance, it can use it to both import data from and export data to physical tape.
Before a physical tape library can be added to the configuration of the NearStore VTL appliance, it must first be connected to the system and powered on as outlined in the NearStore VTL Installation and Setup Instructions.
If no physical tape devices are displayed on the Add Physical Tape Devices screen, click Discover to scan for them.
A physical tape library is typically composed of a number of physical tape drives and a media changer. Before the NearStore VTL appliance can work with these devices, they must be associated with each other (as a library) and then added to the system's configuration.
When you add a physical tape library to the NearStore VTL appliance, the NearStore VTL automatically associates the drives and the media changer. If the physical tape library supports SCSI device serialization, this process is rapid. If the physical tape library does not support SCSI device serialization, this process can take some time to complete.
If you are adding a replacement physical tape drive to an existing physical tape library, the NearStore VTL associates the new drive with the media changer of the physical tape library in which it is installed.
Complete this task to add physical tape libraries to the NearStore VTL:
From the Configuration Tasks menu, located on the left side of the screen, click the Physical Tape Devices task category.
Click the Add Physical Tape Devices tab, located in the upper portion of the screen.
The Add Physical Tape Devices screen appears, and the NearStore VTL displays the physical tape library as a number of individual tape (SCSI/Fibre Channel) devices.
Stand-alone tape devices are displayed as a single device.
Action—provides an option to either add or hide the physical tape device.
Nickname—gives the nickname of the physical tape device.
Port Name—describes the port to which the physical tape device is connected to the NearStore VTL appliance.
Serial Number—provides the serial number for the physical tape device.
In the Action field of each physical tape device that makes up the physical tape library, click Add. Select all the drives if you are adding a library.
If you select Hide, the physical tape devices are no longer displayed on the Add Physical Tape Devices screen.
The physical tape library is added to the configuration of the NearStore VTL. The time that it takes for the NearStore VTL to associate the selected physical tape devices and add them to its configuration depends on whether the physical tape library supports SCSI device serialization. When added, the physical tape library will be displayed on the Physical Tape Device List screen.
At some point it might become necessary to perform maintenance on the tape drives that are connected to the system. Because the NearStore VTL enables tape drives when you add them to its configuration, you will have to disable a drive before you attempt to perform maintenance on it. When a tape drive is disabled, the NearStore VTL does not try to access it.
You can also disable a faulty drive that you do not want the NearStore VTL to use. Before the NearStore VTL can use the tape drive again, you will have to enable it. If you have to replace a tape drive, you must first drop it from the system. see Dropping Physical Tape.
A physical tape device cannot be disabled while it is in use.
Complete this task to enable or disable physical tape devices:
From the Configuration Tasks menu, located on the left side of the screen, click the Physical Tape Devices task category.
Click the Enable/Disable Physical Tape Device tab, located in the upper portion of the screen.
The Enable/Disable Physical Tape Devices screen appears, and the NearStore VTL displays the physical tape devices that have been added to its configuration.
The Status field displays the current state of the physical tape device.
From the Action field of the physical tape device that you want to enable or disable, click either enable or disable.
The physical tape device is either enabled or disabled. The status of the device is displayed on both the Enable/Disable Physical Tape Device and the Physical Tape Device List screens.
Before you can safely disconnect physical tape devices from the NearStore VTL appliance, you must first drop them from its configuration.
It is necessary only to drop the media changer when you drop a physical tape library. This is because the tape drives of a tape library are associated with its media changer. Dropping the changer also drops the associated drives.
You can also drop individual drives from the system. This is especially useful if a tape drive in a library with multiple drives fails. You can drop and replace the drive without having to take the library offline.
See Adding Physical Tape Libraries for information on adding physical tape drives to the NearStore VTL.
Complete this task to drop physical tape libraries from the NearStore VTL appliance:
From the Configuration Tasks menu, located on the left side of the screen, click the Physical Tape Devices task category.
Click the Drop Physical Tape Device tab, located in the upper portion of the screen.
The Drop Physical Tape/Changer Devices screen appears, and the NearStore VTL displays the physical tape devices that have been added to its configuration. The media changer of each virtual library is specified either by its auto-selected or user-defined name. It is also identifiable by its model information.
In the Action field of the media changer that is associated with the physical tape library that you want to drop, click drop.
The physical tape library is dropped from the configuration of the NearStore VTL appliance. The NearStore VTL no longer displays it on the Physical Tape Device List screen.
|
|
 |
|
| Working with RAID Groups |  |
Configuring Miscellaneous Settings |
Copyright © 1994-2005, Network Appliance, Inc. All rights reserved.
Part number 210-02720_A0
Comments