The mainframe — namely the IBM Z platform — has, does, and will continue to play an essential and irreplaceable role in IT infrastructures across the world’s economy. As with any complete IT implementation, an IBM Z on-premises (where the premises can be geographically distributed as necessary) private cloud consists of closely integrated compute, storage, and networking components. On the storage side, IBM offers both random access storage, such as the all-flash DS8000 storage systems, and sequential access storage, such as the TS7700 virtual tape library (VTL).

Now, much attention tends to be paid to random access storage as the active production data, such as for online data processing (OLTP) typically requires random access storage media. Moreover, interactions with random access data tends to be “real-time” and so this is what most people see. However, sequential storage plays vital roles in data protection and business continuance as well as in archiving, migrating HSM (hierarchical storage management) data, as a repository of relevant historical data advanced analytics, and even batch processing (which still exists in some cases, such as payroll processing).

Like other VTLs, IBM’s TS7700 virtual tape system does not have to be all tape. In fact, it can be a combination of tape and disk, or even all disk. As the name “virtual tape” implies, the Z mainframe simply assumes that all the storage that a TS7700 manages is tape so, as a consequence all data is written sequentially.

IBM has just announced TS7700 R4.1.2. This release offers new choices for compression for both older versions of the TS7700 (namely the TS7720 and the TS7740 models) and the current product the TS7760. The release also supports 16 Gb FICON (16 Gbps) to improve the connectivity from the host to a TS7760 only from the previous 8 Gb FICON.

More powerful compression is now available

Compression has long been associated with tape (as well as with virtual tape that includes disk arrays). Not all data can be compressed (notably video files), but redundancies can often be taken out and thus the amount of usable data to the stated nominal capacity of a piece of storage media can be increased.

The famous LZ1 algorithm (from a man named Lempel) is still used as the standard on FICON adapters; IBM feels that this algorithm compresses on average (your mileage may vary) 2.66:1 (say 2.5:1 for simplicity). As an example, after compression 100GB of uncompressed data will take up about 40GB worth of storage media space.

IBM also offers two other standard compression algorithms that go by the names of LZ4LZ4 and ZSTD. Both are software-based (which means that no additional hardware is needed). However, as software runs on processors, some of the CPU cycles on the TS7700’s server has to be used. IBM feels that the impact of these workloads is negligible for the newer processors on the server portion of a TS7760, but may have a small impact on older non-TS7760 systems.

In any event, an IT organization can choose to run any combination of LZ1, LZ4, ZSTD, or no compression. The rules are that all TS7700 systems that are managed together (as clusters in a grid arrangement) have to be running R4.1.2 and that all data that is designated as a DATACLASS has to use the same compression method for the logical volumes where the data resides.

The net result is that IT organizations may be able to achieve up to a 5:1 instead of a 2.5:1 compression ratio. If a company used all disk and maxed out on a single TS7760 repository, that means that 2.45 PB could hold over 12 PB of user data. Note that an IT organization can potentially double its VTL storage. How often in life do you get to double the value of your IT investment for next to nothing?

Improved Performance for TS7760 Virtual Tape Systems

The addition of 16 Gb FICON adapter capability combined with the use of 5:1 compression raises throughput from 2.5 GB/s to over 4 GB/s on TS7760 models. While not as dramatic as the enhancements in compression, this is still a significant improvement. And when dealing with the large volumes of data that is stored on a TS7760, the benefits can be especially welcome in getting critical tasks, such as backing up and migrating HSM data, done in less time (as days are still 24 hours).

Mesabi musings

VTLs are not glamorous. Neither are 18 wheelers, but just as 18 wheelers perform vital economic heavy lifting functions for a wide array of businesses, so do VTLs perform heavy lifting tasks, such as data protection, for mainframe IT infrastructures. IBM has paid attention to the basics in enhancing its TS7700 virtual tape systems. Providing the opportunity for better use of existing storage capacity through using one of two now-made-available compression algorithms delivers economic benefits, such as better utilization of its current storage environment. That will be welcomed by IT executives who always seem to be challenged with ongoing cost pressures. Speeding up the protection of sensitive data through the use of 16 Gb FICON is another valuable performance addition that TS7700 users will appreciate. The TS7700 demonstrates IBM’s ongoing efforts to improve life/value for enterprise customers, especially those who have invested in the Z mainframe platform.