The challenges and opportunities of tape automation.
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.
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.
This is true with technologies such as Fibre Channel. Fibre Channel connectivity is gaining more acceptance in IT environments ranging from the enterprise to the mid-range. Mid-range IT managers demand that drive and library manufacturers offer the same features and functionalities available in enterprise solutions. Manufacturers must meet this demand to remain competitive. Library manufacturers are seizing the opportunity of Fibre Channel to build solutions that are larger and faster as well as easier to implement and manage. However, Fibre Channel raises integration challenges to a completely new level. Fibre Channel can be implemented at the drive level in many ways: Either native, built into the drive's interface; through a bridge or converter to the drive; or in a router. Native implementations, like the Mammoth-2 (M2), are easier to integrate into a FibreChannel library environment, because they bypass the compatibility and integration issues that arise whenever a new link is added to the chain. The result is easier operation and easier maintenance.
There Is No Server Like "No Server"
Fibre Channel at the drive level also opens new possibilities to automation vendors with advanced connectivity protocols like SNIA's Extended Copy (eCopy). With eCopy, a library can perform serverless backup. The result can be huge savings in network equipment expense and server cycles, as well as reduced backup windows and faster restore times. However, eCopy presents the library builder with another dilemma, namely, where should the eCopy functionality reside? In the drive? In the library? Or in an external switch or router'? In beta tests of embedded eCopy with Mammoth-2 (M2) native FibreChannel drives, the server utilization needed for a backup drops down to just a few percent--from 20% to 40% utilization in a "normal" backup. Not only that, eCopy embedded in the drive also allows each drive in a library to perform close to its peak transfer rate, without any bottlenecks. This kind of enhanced performance and cost savings make native eCopy drives an excellent choice for automation manufacturers. With mainstream software support for eCopy around the corner, this functionality will be available later this year.
Data Management, Not Storage
When it comes to managing data, IT administrators want it easier, more reliable, and less costly. They demand the most functionality, in the smallest amount of space, at the best value. Buzzwords like usability, availability, manageability, reliability, upgradability, flexibility, density, affordability, and connectivity are now ingrained into the IT consciousness, and seem to override the traditional capacity and performance requirements.
The days of single-technology automation vendors are gone. The proliferation of tape technologies has brought with it a user demand for the right to choose. Paradoxically, users have also become technology agnostic. Important usability features like bar code readers for enhanced media management, user-friendly, intelligent interfaces, and easily accessible drives and media do depend on the choice of drive technology. The capability to manage and monitor systems remotely from anywhere in the world increases efficiency, improves uptime, and reduces costs. Virtual Storage Management, or the ability to partition a large library into a series of smaller libraries, is another key consideration. Fail-safe design features, like redundant tape drives, redundant power and hot swappable drives, provide higher data reliability and availability and have become part of the mainstream feature mix for library manufacturers.
There is not one of today's tape library manufacturers who does not face many, if not most, of these decisions, dilemmas, and challenges. Throughout its unique 15-year history of tape technology innovation and engineering, Exabyte has faced these kinds of choices repeatedly--beginning with the EXB-10, the first midrange tape library introduced in 1989. Then, as now, the real challenge was in bringing a divergent universe of options into powerful, reliable, and efficient tape automation solutions. How tape drive manufacturers meet this challenge is of far greater concern to users than simple mechanics.
Kelly Beavers is the vice president of marketing at Exabyte Corp. (Boulder, CO).
|Printer friendly Cite/link Email Feedback|
|Title Annotation:||Tape/Disk/Optical Storage|
|Publication:||Computer Technology Review|
|Date:||Jan 1, 2002|
|Previous Article:||Eliminating the reel motor position sensor in a tape drive.|
|Next Article:||Database strategy: active archiving.|