The TS7700 Virtualization Engine, introduced in 2006, is the fourth generation of IBM Tape Virtualization products for mainframes. It replaces the highly successful IBM TotalStorage Virtual Tape Server (VTS).

This chapter includes the following sections:

This publication explains the new features introduced with the TS7700 Virtualization Engine Release 3.1, and the concepts associated with it. TS7700 Release 3.1 can be installed only on TS7720 Model VEB and TS7740 Model V07. Release 3.1 is not supported on the previous generation of TS7700 models: TS7740 Model V06 and TS7720 Model VEA.

The TS7700 Virtualization Engine is a modular, scalable, and high performing architecture for mainframe tape virtualization. It incorporates extensive self-management capabilities consistent with IBM Information Infrastructure initiatives. These capabilities can improve performance and capacity. Better performance and capacity help lower the total cost of ownership for tape processing and help avoid human error. A TS7700 Virtualization Engine can improve the efficiency of mainframe tape operations by efficiently using disk storage, tape capacity, and tape speed. It can also improve efficiency by providing many tape addresses.

The TS7700 Virtualization Engine uses outboard policy management functions to manage the following key features:

The engine also includes a new standards-based management interface and enhanced statistical reporting.

TS7700 Virtualization Engine provides tape virtualization for IBM System z servers. Tape virtualization can help satisfy the following requirements in a data processing environment:

TS7700 Virtualization Engine Release 3.1 delivers the following capabilities:

A virtual tape subsystem presents emulated tape drives to the host and stores tape data on emulated tape volumes. These volumes are in a disk-based cache rather than physical tape media. The TS7700 Virtualization Engine emulates the function and operation of IBM 3490 Enhanced Capacity (3490E) tape drives. It uses a RAID technology disk subsystem to store volumes written by the host. The disk space provided is called a Tape Volume Cache (TVC).

The main components of the TS7700 Virtualization Engine are shown in Figure 1-1.

Emulated tape drives are also called virtual drives. To the host, virtual 3490E tape drives look the same as physical 3490E tape drives. Emulation is not apparent to the host and applications. The host always writes to and reads from virtual tape drives. It never accesses the physical tape drives (commonly referred to as the back end tape drives) attached to TS7740 Virtualization Engine configurations. In fact, it does not need to know that these tape drives exist. Even an application that supports only 3490E tape technology can use the TS7700 Virtualization Engine without any changes. Therefore, the application benefits from the high capacity and high performance tape drives in the back end. For TS7720 Virtualization Engine configurations, no physical tape attachment exists. However, the virtual tape drives work the same for the host.

Because the host exclusively accesses the virtual tape drives, all data must be written to or read from emulated volumes in the disk-based TVC. These emulated tape volumes in the TVC are called virtual volumes.

When the host requests a volume that is still in disk cache, the volume is virtually mounted. No physical mount is required. After the virtual mount is complete, the host can access the data at disk speed. Mounting scratch tapes is also virtual and does not require a physical mount.

Although you define maximum sizes for your volumes, a virtual volume takes up only the space in cache that the compressed data on the volume actually requires. For this reason, tape virtualization makes efficient use of disk capacity. In TS7740 Virtualization Engine configurations, the virtual volumes are copied from disk to tape. They also need only the amount of tape capacity occupied by the data that is stacked end-to-end, making efficient use of disk and tape capacity.

Another benefit from tape virtualization is the large number of drives available to applications. Each TS7700 Virtualization Engine provides you with a maximum of 256 virtual tape devices. Often, applications contend for tape drives, and jobs must wait because no physical tape drive is available. Tape virtualization efficiently addresses these issues by providing many virtual tape drives.

The TS7740 Virtualization Engine manages the physical tape drives and physical volumes in the tape library. It also controls the movement of data between physical and logical volumes.

In the TS7740 Virtualization Engine, data written from the host into the TVC) is scheduled for copying to tape later. The process of copying data to tape that only exists in cache is called premigration. When a volume is copied from cache to tape, the volume on the tape is called a logical volume. A physical volume can contain many logical volumes. The process of putting several logical volumes on one physical tape is called stacking. A physical tape containing logical volumes is therefore referred to as a stacked volume. This concept does not apply to TS7720 Virtualization Engine because no physical tape devices are attached to it.

In the TS7740, many applications are unable to fill the high capacity media of modern tape technology, you can end up with many underused cartridges. This wastes much space and requires an excessive number of cartridge slots. Tape virtualization eliminates any unused volume capacity and fully uses physical tape capacity when present. Also, tape virtualization allows you to use the full potential of modern tape drive and tape media technology. In addition, it does so without changes to your applications or JCL.

When space is required in the TS7740 Tape Volume Cache for new data, volumes that already have been copied to tape are removed from the cache. By default, removal is based on a least recently used (LRU) algorithm. Using this algorithm ensures that no new data or recently accessed data is removed from cache. The process of deleting volumes in cache that have been premigrated to tape is called migration. Volumes that have been deleted in the cache and exist only on tape are called migrated volumes. In a TS7720 Virtualization Engine configuration, no migrated volumes exist because there is no physical tape attachment. Instead, logical volumes are maintained in disk until they expire. For this reason, cache capacity for the TS7720 Virtualization Engine is larger than the capacity for the TS7740 Virtualization Engine.

When a TS7720 Virtualization Engine is a member of a multicluster hybrid grid, virtual volumes in the TS7720 Virtualization Engine cache can be automatically removed. This removal is done by using a Volume Removal Policy if another valid copy exists elsewhere in the grid. A TS7700 grid refers to two or more physically separate TS7700 clusters that are connected to one another by using a client-supplied Internet Protocol network.

On the TS7740 Virtualization Engine, a previously migrated volume must be copied back from tape into the TVC to be accessed. It must be copied because the host has no direct access to the physical tapes. When the complete volume is copied back into the cache, the host can access the data. The process of copying data back from tape to the TVC is called recall.

Figure 1-2 shows TS7740 Tape Volume Cache processing.

With a TS7720 tapeless virtualization engine, the virtual volumes are accessed by the host within the TVC.

Figure 1-3 shows the TS7720 Tape Volume Cache processing.

Another benefit of tape virtualization is the data replication functionality. Two, three, four, five, and six TS7700 Virtualization Engines can be interconnected. The connections can be through one of the following sets of links:

These sets of links form a multicluster grid configuration. Adapter types cannot be mixed in a cluster. They can vary within a grid depending on your network infrastructure. Logical volume attributes and data are replicated across the clusters in a grid. Any data replicated between the clusters is accessible through any other cluster in the grid configuration. Through remote volume access, you can reach any virtual volume through any virtual device. You can reach volumes even if a replication has not been made.

Setting policies on the TS7700 Virtualization Engines defines where and when you have multiple copies of your data. You can also specify for certain kinds of data, such as test data, that you do not need a secondary or tertiary copy.

You can group clusters within a grid into families. Grouping allows the TS7700 to make improved decisions for tasks, such as replication or TVC selection.

Depending on the configuration, multiple TS7700 Virtualization Engines that form a grid provide the following types of solutions:

A multicluster grid configuration presents itself to the attached hosts as one large library with the following maximums:

The copying of the volumes in a grid configuration is handled by the clusters, and it is not apparent to the host. By intermixing TS7720 and TS7740 Virtualization Engines, you can build a hybrid two, three, four, five, or six-cluster grid.

Figure 1-4 shows multiple TS7700 Virtualization Engine Grids in an example of possible host and grid connections.

For TS7740 Virtualization Engine Grid configurations, each TS7740 Virtualization Engine manages its own set of physical volumes. The TS7740 maintains the relationship between logical volumes and the physical volumes on which they are located.

The clusters in a TS7700 grid can, but do not need to be, geographically dispersed. In a multiple cluster grid configuration, two TS7700 clusters are often located within 100 km
(62 miles) of each other, whereas the remaining clusters can be located more than 1,000 km (621.37 miles) away. This configuration provides both a highly available and redundant regional solution while also providing a remote disaster recovery solution outside of the region.

A multicluster grid supports the concurrent growth and reduction of cluster counts.

The current global marketplace is increasingly information-oriented, which has far-reaching implications for businesses. The ability to securely use information can create a competitive advantage. The following information-related business trends are causing an explosion of information and complexity in data centers:

IBM offers an extraordinary range of systems, storage, software, and services that are based on decades of innovation. This range is designed to help you get the right information to the right person at the right time. It also manages challenges, such as exploding data growth, new applications, dynamic workloads, and new regulations.

IBM Information Infrastructure intelligently stores, retrieves, protects, and distributes information to help you get a competitive advantage. Converting data centers to service-oriented architectures (SOAs) means that multiple service levels are identified and supported, including information services. Certain information services must be high speed to support websites and databases. In some cases, information services must be multiplexed to multiple locations, or require extra encryption and overwrite protection. IBM Information Infrastructure helps you apply the correct services and service levels so vital information can be delivered.

IBM Information Infrastructure solutions are designed to help you manage this information explosion. They also address challenges of information compliance, availability, retention, and security. This approach helps your company move toward improved productivity and reduced risk without driving up costs.

The TS7700 Virtualization Engine is part of the IBM Information Infrastructure. This strategy delivers information availability, supporting continuous and reliable access to data. It also delivers information retention, supporting responses to legal, regulatory, or investigatory inquiries for information.

The TS7700 Virtualization Engine can be the answer to the following challenges:

You can expect the following types of benefits from tape virtualization:

TS7700 Virtualization Engine R3.1 documentation displays data storage values using both decimal (base-10) prefixes and binary (base-2) units of measurement.

Decimal units, such as KB, MB, GB, and TB, are commonly used to express certain values. However, the base of the units can be misleading. To prevent confusion, IBM uses a convention to differentiate between binary and decimal units. At the kilobyte level, the difference between decimal and binary units of measurement is relatively small (2.4%). This difference grows as data storage values increase. When values reach terabyte levels, the difference between decimal and binary units approaches 10%.

Both decimal and binary units are available throughout the TS7700 Tape Library documentation. Table 1-1 compares the names, symbols, and values of the binary and decimal units.

Table 1-2 shows the increasing percentage of difference between binary and decimal units.