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Chapter 2. Configuring a NearStore VTL Appliance | 
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| Advanced Configuration | ||
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Chapter 2. Configuring a NearStore VTL Appliance |
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This section provides information that you can use to perform a more advanced configuration of the NearStore VTL appliance. This includes the advanced configuration options that are listed in the Configuration Road Map. You can also use the information provided in this section to fine-tune the configuration as your requirements change.
The configuration process for advanced features depends on the features that you choose. For example, if you are going to use physical tape validation, all you have to do is enable it. The NearStore VTL does the rest. If, on the other hand, you want to use customer accounts, you must enable the feature, create one or more accounts, and then add virtual libraries to them.
For this reason, this section provides a subsection that outlines a generic process that you can use to enable advanced configuration features. This also includes overview information for each feature, including whether additional setup is required after a given feature is enabled.
Advanced configuration subsections include:
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:
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 Working with Customer for more information.
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.
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.
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 Using Physical Tape Pick Lists.
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 Working with Port Assignments for more information.
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 Working with Virtual Libraries for more information.
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 Working with Physical Tape Libraries/Devices.
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:
From the Configuration Tasks menu, located on the left side of the screen, click the Advanced task category.
The Options Screen appears and the NearStore VTL displays the advanced configured options that are available.
Select the advanced configuration option(s) that you want to enable. This example enables the Use Customer option.
If you are enabling deferred cloning, you must select the times during which you do not want the NearStore VTL to clone virtual tapes.
Click Apply to enable the advanced configuration option(s) that you selected.
A storage pool is comprised of one or more RAID group disks that are grouped together to provided a specific amount of storage resource. At its most basic level, a storage pool is created when the first RAID group is added to the NearStore VTL. This is called the default storage pool.
Unless the option to use storage pools is enabled, the NearStore VTL adds each additional disk to the default storage pool. Once you have added a disk to the NearStore VTL, you cannot move it to another storage pool.
When you enable the Use Storage Pool option, you can create multiple storage pools and then add physical disks to them.
In order to use a storage pool, you must first associate at least one physical disk with it.
You must enable the Use Storage Pools option before you can create storage pools and add physical disks to them. See Enabling Advanced Configuration Features for more information.
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 Working with Physical Tape Libraries/Devices .
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.
A virtual tape drive type that is in use cannot be modified or used to create a custom virtual tape drive type.
Creating Virtual Tape Drive Types
Complete this task to create/edit virtual tape drive types:
From the Configuration Tasks menu, located on the left side of the screen, click the Advanced task category.
Click the Virtual Tape Drive Types tab, located in the upper portion of the screen.
The Virtual Tape Drive List screen appears and the NearStore VTL display the virtual tape drive types that are currently available.
Invoke the Add Virtual Tape Drive Type screen.
Click the name of a virtual tape drive to use it as a model for the creation of a new virtual tape drive type.
When using an existing virtual tape drive type as a model, ensure that you change the name specified in the Virtual Tape Drive Type Name field. Failure to do this could overwrite the existing type.
Select Define New Virtual Tape Drive Type.
The Add Virtual Tape Drive Type screen appears. If you selected an existing virtual tape drive type, the Update Virtual Tape Drive Type screen appears and the fields will be filled in with the parameters of that type. If you chose to define a new virtual tape drive type, the fields will be empty. This example uses the Add Virtual Tape Drive Type screen.
Complete the following configuration parameters for the new virtual tape drive type. You can also modify the parameters of an existing virtual tape drive type.
Virtual Tape Drive Type Name—specifies the name of the virtual tape drive type.
Raw Capacity—gives the capacity of the virtual tapes that are supported by the virtual tape drive type.
Disk Allocation Per Tape—provides the maximum disk space (GB) reserved for this virtual tape.
Vendor Id—provides the vendor identification by which this type of virtual tape drive identifies itself on the SAN. The vendor identification is important because it is used by the backup application to identify the virtual tape drive.
Product Id—gives the product identification by which this type of virtual tape drive identifies itself on the SAN. The product identification is important because it is used by the backup application to identify the virtual tape drive.
(Optional) Tape Optimization—provides a drop-down menu from which you can select the type of tape optimization support that you want to enable for the virtual tape drive type.
If you select NONE, the virtual tape drive type will not support tape optimization. This means that any virtual libraries that use this drive type will not support tape optimization.
When you are finished defining the parameters of the new virtual tape drive type, click Apply.
The NearStore VTL adds the new virtual tape drive type. If you modified an existing virtual tape drive type, the NearStore VTL saves these changes. You can use them to create new virtual libraries.
The NearStore VTL virtual libraries are implementations of specific virtual library types. Library types define things such as the number and capacity of virtual tape drives and whether the virtual library supports compression.
The virtual tape drives that are associated with virtual libraries are also defined by type. The virtual tape drive type defines the capacity of the tape and whether or not it supports tape optimization. Virtual tape drive types also provide vendor and product information.
Both virtual library and tape drive types provide vendor and product information for the backup application.
Default and Custom Virtual Library Types
The NearStore VTL comes with a number of default virtual library types. You can use these default virtual library types to create virtual libraries, or you can use them as models for custom virtual library types.
A virtual library type that is in use cannot be modified or used to create a custom virtual library type.
If you have enabled the tape optimization functionality of the system, you will have to create a virtual tape drive type that supports this feature. Then you will have to select this virtual tape drive type when you create the virtual library type.
See Enabling Advanced Configuration Features for more information on using tape optimization.
See Creating/Editing Virtual Tape Drive Types for more information on creating virtual tape drive types.
Creating Virtual Library Types
Complete this task to create virtual library types:
From the Configuration Tasks menu, located on the left side of the screen, click the Advanced task category.
Click the Virtual Library Types tab, located in the upper portion of the screen.
The Virtual Library Type List screen appears and all of the virtual library types that have been configured for the NearStore VTL appliance are displayed.
Invoke the Add Virtual Library Type screen.
Click the name of a virtual library to use it as a model for the creation of a new virtual library type.
When using an existing virtual library type as a model, ensure that you change the name specified in the Virtual Library Type Name field. Failure to do this could overwrite the existing type.
If you are going to create a virtual library type without using an existing virtual library type as a guide, click Define New Virtual Library Type.
If you are creating a new virtual library type, the NearStore VTL will display the Add Virtual Library Type screen and the fields will be blank.
If you are using an existing library type as an example, the NearStore VTL will display the Update Virtual Library Type screen and the fields will contain the parameters from the existing virtual library type.
If you use an existing library type as a model for a new type, change the name of the type (in the Virtual Library Name field) before changing any of the other parameters. This will ensure that you do not overwrite the parameters of the existing library type.
Complete the following configuration parameters for the new virtual library type by either editing the values of the existing virtual library type or by entering new configuration parameters.
Virtual Library Type Name—gives the name of the new virtual library type. For example 8110 is the name of a default the NearStore VTL virtual library type. When using an existing virtual library type as a model, the name must be changed.
Vendor Id—provides the vendor identification by which this type of virtual library identifies itself on the SAN.
Product Id—gives the product identification by which this type of virtual library identifies itself on the SAN.
Virtual Tape Drive Type—provides a drop-down menu from which virtual tape drive types can be selected. Like virtual library types, the NearStore VTL provides a number of default virtual tape drive types. Addition virtual tape drive types can be created.
If you have enabled the over allocation/tape optimization functionality, the drive that you select must support compression.
Automatically Assign First Values— if this option is selected, the NearStore VTL will automatically assign the SCSI element addresses for the components of the virtual library. You should select this option in most cases. If you do not select this option, you will need to specify the starting SCSI element addresses for slots, drives, mailboxes and transports.
Slot Count—specifies the number of slots that the virtual library type will have.
First Slot—specifies the SCSI element address of the first slot in the virtual library. The NearStore VTL will automatically select this value if you enable Automatically Assign First Values.
Drive Count—specifies the number of virtual tape drives that the virtual library type will have.
First Drive—specifies the SCSI element address of the first virtual tape drive in the library. The NearStore VTL will automatically select this value if you enable Automatically Assign First Values.
Mailbox Count—specifies the number of mailboxes that the virtual library type will have.
First Mailbox—specifies the SCSI element address of the first mailbox (I/O port) in the virtual library. The NearStore VTL will automatically select this value if you enable Automatically Assign First Values.
Transport count—describes the number of transport mechanisms (such as mechanical arm) in the virtual library.
First transport—in the case of multiple transports, describes which transport is first. You can either have the NearStore VTL assign this value, or you can enter it manually if the values of the physical tape library are hard coded.
Constrain Volume Labels—enables you to define which part of the label (virtual barcode) increments as the NearStore VTL creates new virtual tapes. You do this by defining the digits/characters that do not increment as the label prefix and the label suffix.
This is useful if you are using barcodes with a prefix and/or a postfix that does not increment.
Label Length—gives the total number of digits or characters in the label, including the prefix and postfix
Label Prefix—specifies the digits or characters that are used as the label prefix.
Label Postfix—provides the digits or characters that are used as the label postfix.
When you are finished defining the parameters of the new virtual library type, click Apply.
The new virtual library type is added to the configuration of the system. You can use them to create new virtual libraries.
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| Configuring Miscellaneous Settings |  |
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