The challenges and opportunities of tape automation - Tape/Disk/Optical Storage

Computer Technology Review, Jan, 2002 by Kelly Beavers

As data creation, consumption, and value continues to grow, the need for storage automation solutions becomes increasingly critical. Beginning with the IBM 726, the first tape drive introduced in the early 1950s, tape has presented users with the most efficient and affordable option for offline storage. The advent of tape automation robotics in the 1970s raised tape to new levels of functionality. Today, advances in robotics and connectivity are boosting the new generation of tape automation to new heights of power and efficiency, at a lower cost of ownership.

Tape libraries are designed around high-performance tape drives like Mammoth, AIT, DLT, and LTO. When integrating these drives, tape library manufacturers face unique challenges and opportunities, ranging from spatial design issues that affect storage density, to seemingly trivial matters like cabling and grounding, to the particularly technical challenges in connectivity and networking.

Density: The Storage Crunch

In today's cramped data centers, real estate is at a premium, and maximum storage density is a necessity. Compact, space-efficient drives, like 8mm Mammoth and AIT, let library manufacturers pack the maximum number of tape drives and cartridges into the smallest library space. Half-inch drives, like DLT and LTO, are much larger, and use larger cartridges. For example, the Exabyte 215M, a MammothTape library, packs two drives and 15 cartridges into the same enclosure as the Exabyte 110L, which offers just one LTO drive and 10 cartridges. As an added dimension, within the same physical space, and with two drives, the MamothTape library offers a higher level of functionality than the single-drive LTO autoloader. The advantages can be even greater with larger scale systems.

Robotics: The Right Touch

Tape cartridges are all different. Compared to a light, compact 8mm cartridge, a DLT cartridge is larger and heavier. The two also differ in handling, loading, and unloading characteristics. This places a wide range of demands on the robotic grippers within a library. It also presents manufacturers with the dilemma to either design a different gripper for each tape technology, or to minimize design, engineering, and manufacturing costs by developing flexible gripping mechanisms that can accommodate the different cartridge sizes, weights, and designs.

The robotic challenge is compounded because each tape drive technology differs in how it accepts and ejects a tape. Some tape drive technologies use a soft load mechanism while others use a latch load. The insertion force needed from the robotic mechanism to insert a tape into the tape drive varies between drives. Cartridge ejection distances also differ. Drive doors are not all located in the same location, and even drives of the same technology (i.e. LTO) do not operate in the same manner. Library manufacturers must account for these differences when planning the entire robotic mechanism.

Drive power and cooling requirements, differences in cabling, drive communication protocols, drive emissions, and sensitivity to ESD (electrostatic discharge) are other factors that present challenges to library manufacturers. Without careful grounding and/or isolation, the robotics can produce currents that might create error rates in the drives. Cooling and power are significant issues, particularly in larger libraries with multiple drives. MammothTape drives, for example, consume as little as 15 watts, whereas a DLT drive may consume as much as 60 watts. Drives with higher power consumption need cooling fans, which can create acoustic noise that could lead to certain reliability issues. Additionally, some of the higher transfer rate tape drives require special shielding and/or cabling to control emissions.

Multi-Technology: Too Many Cooks ...

Some library vendors promote the ability of a single library to handle multiple tape drive technologies simultaneously. In addition to hardware challenges, this approach creates software issues. Which cartridges belong to which drives? Will an error-prone human operator install a cartridge in the wrong slot? Must the cartridges all be imported through the entry port? How does the application identify a particular type of media? All of these issues lead to confusion and errors. In the end, users find that mixing technologies within one library is actually an inefficient way to manage data. Of far higher value is a common design concept that creates usage and feel similarities, regardless of the library tape drive technology. This reduces the time and money needed to qualify a solution within its environment.

Networks: Connect-The-Dots

Another key challenge is for products to offer maximum connectivity. Environments vary widely, based on server platforms, operating systems, software applications, and other computer components. Exabyte product teams never stop evaluating new technology trends, with the objective of deploying the industry's fastest, most efficient, and reliable interface from the host system to the tape library. Automation manufactures must also invest in testing their products with other storage components to ensure connectivity, interoperability, compatibility, and ease of configuration.