Feature

Make tape libraries work with all platforms

Ezine

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VIRTUALIZE TAPE DEVICES

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Centralized and heterogeneous tape virtualization enables the consolidation of multiplatform tape configurations where common backup/archiving policies can be set, tape devices can be managed easily and physical resources can be shared more effectively.

Limits to tape sharing
The key to tape sharing is the ability to establish static mount points so that only one system can read/write to one tape at a time. The process of mounting/dismounting tape drives is time consuming. With disk arrays, several hosts can simultaneously access a set of disks and while each obtains the data it requested, the context switching is transparent to the host. This is impossible with current tape technologies because when host systems need access to the same set of tapes or tape drives, each must wait until the previous request has completed. In this scenario, aggregate data rate transfers drop dramatically, often to fewer than 100KB/sec.

Another operational risk for arrays and ATLs posed by multiplatform support is the need to quiesce the system to update microcode. When this occurs, some or all of the attached hosts are affected. Each attempt to upgrade shared ATLs or tape drives requires coordination among mainframe, Unix and Windows groups. Array vendors have overcome this limitation by minimizing or eliminating disruptive microcode upgrades so that elaborate coordination is no longer necessary.

Even sharing ATLs among open systems can be difficult. Brian Estes, lead systems engineer at James Madison University, Harrisonburg, VA, has Unix, Windows and NetWare in his shop. "We haven't had much luck with integrating NetWare into our Unix/Windows backup environment," he says. "We tried a couple times, but the backups become unstable when ATL changes are made so we had to segment NetWare from other systems."

Solving the problem
Last year, the Meta Group Inc. (now part of Gartner Inc.), Stamford, CT, published "Tape Storage Virtualization--A New & Valuable Approach to Improve Data Center Efficiency." This whitepaper offers benchmarks to determine when an operation merits consolidation of open systems and mainframe tape configurations.

TYPICAL DATA CENTER TAPE LIBRARY ENVIRONMENT

In most data centers, tape resources are dedicated to specific host platforms. Sharing tape drives could significantly reduce costs.

According to Meta Group, a dramatic cost reduction may be realized if mainframe and open-systems tape can be centrally managed. There are some effective solutions--for example, Fujitsu Siemens' CentricStor and Neartek Inc.'s Virtual Storage Engine support all major platforms simultaneously. Neartek even extends this support to include legacy platforms like AS/400, Unisys mainframes and Hewlett-Packard MPE servers.

These products emulate all the major enterprise tape drive mount types, connect to major storage arrays and support the most popular host processing platforms. They provide impressive cross-platform functionality that many users would rather see delivered natively by the tape library and drive vendors. Instead, to achieve an effective consolidation of enterprise tape environments and to recover costs through improved use of physical assets, users have to purchase the additional virtualization "engines." Interestingly, the engines commoditize the ATLs, which become passive recipients of data streams as the virtualization engine handles all management functions (see "Virtualize tape devices," above).

Tape-sharing solutions for multiplatform environments will enable standardized, enterprise-wide backup and recovery, and reduce the number of storage devices required. Nirvana will be achieved when users can take any library, plug it into any multiplatform host environment and back up any system with a tool that migrates old data to the new environment seamlessly.

This was first published in November 2005

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