Tech Primer

Automated Tape Libraries

What are ATLs?

ATLs are integrated hardware and software systems designed to provide automated access to terabytes-to-petabytes of data resident on magnetic tape cartridges without a human tape librarian being required to physically mount a tape in a drive when some user or process needs it. ATLs are used extensively as enabling hardware in back-up and recovery systems, as well as tape-based nearline storage systems such as hierarchical storage management.

Why has there been an increase in demand for ATLs?

Network storage requirements have exploded in the last few years, and the trend shows no signs of abating. Several market trends and technologies have combined to fill server discs, seemingly as fast as they can be added on. While the requirements have certainly increased, the resources of system and network administration have not kept pace. The solution was to bring in automated back-up by bringing in ATLs.

What are the benefits of ATLs?

ATLs reduce human intervention. By doing so, labour needs are decreased, as also the opportunity for human error. If configured properly, an automated library system is not likely to use the wrong tape for a store, nor fail because the right tape wasn’t available keeping in mind that the main reason for performing back-ups has switched from protection from hardware failure to protection from human error. Another benefit to automating back-ups with a library is centralised data control. Aggregating back-up data and its media in libraries allows system administrators to establish and enforce company policies and procedures for back-up and security. ATLs also help in reliability. A failure to load the tape may not require service on the hardware, but it could easily preclude a whole night’s back-ups. Intervention then becomes necessary not only to fix the device but also to fix the back-up schedules.

What are the common attributes in an ATL?

Most ATL’s share a common set of attributes irrespective of the vendor, model and configuration. ATLs come in a wide variety of capacity points, from tens to tens of thousands of slots. In ATLs, media often feature pre-set or manually-added barcode labels to help the library determine the unique identity of each media. An ATL also has a robotic mechanism, or picker, that moves tapes from slot to drive, slot to slot, and slot to Cartridge Access Ports (CAPs). By and large, this is the automation part of ATL. CAPs act as import-export mechanisms to add or remove tapes from the library non-disruptively.

What is the pass-through mechanism and library control system in an ATL?

In libraries that scale or expand by plugging multiple modular library storage components together, a mechanism is often needed to allow passing of tapes between modules; these are generally referred to as ‘pass-through ports.’ A library control system is a hardware and software glue that helps the slots, drives, pickers, caps and everything else in the library work as a cohesive whole as opposed to allowing the picker to start tearing holes in the side of the library. The library control system generally provides some kind of interface to the ‘outside world’ to allow control of the library by third-party software, either via the standard autoloader SCSI command sets, or via a vendor-specific LAN-enabled API (such as those offered by StorageTek, ADIC and IBM). In addition to controlling the library, a major function of the library control system is determining the media contents of the ATL based on barcode / media ID. In most cases today, the set of functions / tools providing comprehensive library control is shared between stuff provided by the library vendors and third-party software products using the library for a purpose. This point is important because an ATL on its own, without any additional supporting system or software, is generally devoid of purpose.

Can ATLs be partitioned?

Some ATLs offer the ability, in ‘hardware,’ to be partitioned into multiple independent physical libraries, each containing a distinct set of tape drives and cartridge slots. This can be handy in cases where one physical library resource may need to be leveraged by multiple systems.

Is external software required to put ATLs to work?

Although ATLs are becoming increasingly smarter, an external software or data management framework is almost always required to put the library to work, examples being tape back-up products such as EMC/Legato NetWorker, Veritas NetBackup and Backup Exec, IBM Tivoli Storage Manager, CommVault and BakBone.

Who are the prominent ATL vendors in the market?

IBM, StorageTek (now Sun), HP, SpectraLogic, Quantum, ADIC.

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