Tape libraries central to intelligent tape: tape proves its value in data center, disaster recovery - Storage Management

Computer Technology Review, Nov, 2003 by Christine Taylor Chudnow

Storage vendors are pushing to add more and more intelligence to their storage devices and components. Infrastructure, arrays, software-based management, libraries--developers are working to provide new levels of efficiency, automation and management capabilities at hardware and software levels.

[ILLUSTRATION OMITTED]

Tape is no exception. Tape storage vendors are constantly increasing tape speed and capacity, and are also placing increasing amounts of intelligence and automation into Fibre Channel tape libraries. But is this intelligence being used as well as it could be?

Tape benefits and suffers from the idea that it only does backup and recovery. This is its main job--tape's claim to fame is cost-effectiveness, portability and reliable media. But tape has recently suffered hits from disk backup competitors as users, vendors and the press ask either/or questions: Should everyone back up to disk? (No.) Should some applications back up to disk? (Yes.) Is tape going away? (No.) Is disk going to replace tape? (Not for a long time.)

Why? Since companies can back up to disk (and library developers themselves are putting in disk front-ends), why go with tape? The reason is portability, which is still vital in disaster recovery schemes. Senior analyst Steve Duplessie of the Enterprise Storage Group, commented, "Using inexpensive disks to recover from nondisasters makes sense. But companies will still put a tape backup in a bunker in Provo, Utah, just in case a bomb goes off."

But portability isn't the single reason administrators are still using tapes. IT does get tired of shifting tape around, and many of them long for the ease of disk-based backups. However, the reality is that archival storage still revolves around tape; it retains a huge installed base, remains much less expensive than disk (even serial ATA) and its portability provides high levels of protection and security. (It's really hard for hackers and viruses to attack off-site tape.) These qualities alone will keep tape firmly planted in data centers, and ongoing advances in tape, especially automated management tasks and disk/tape hybrids, will keep tape an important element of the storage networking equation.

Tape libraries are central to intelligent tape. Just as centralized disk arrays are more cost-effective than direct-attached disk, tape libraries are more cost-effective than individual tape drives on individual servers. Since libraries use centralized media, tape owners reduce tape handling and experience more efficient operations, because they don't have to manually switch out tape as often as in smaller libraries and autoloaders. Because libraries are critical for efficient backup operations, developers are placing intelligence in the libraries as well as in individual drives. Intelligent tape includes features like:

Intelligent processor: Most tape library vendors concentrate intelligence in the processor, which should have high speed and vast I/O capability. Recent advances like this allow highend library developers to dispense with external library controllers.

Front-end disk cache: Many enterprise library makers have combined tape and disk subsystems by placing a disk array on the front-end of the tape library. The disk is configured to look like tape so backup applications will write to it, but it captures backup data quickly and archives it at leisure.

High-end tape library: Libraries house many disk drives for high capacity, boasting highly reliable tape drives, robust robotics, and SCSI and FC connectors. Ideally, it should be neutral on the drive and media types it can hold. Several library developers have included internal partitioning capabilities.

Management software: Includes internal management software for system management, external sharing and integration, and diagnostics for SAN management applications such as SRM.

Standards-based: New tape libraries should be SMI-S compliant. SNIA's SMI-S standard is key to for managing communications and integration within heterogeneous storage networks.

Welcome Advances

Several advances have kept tape an important part of the data center, including more sophisticated management software, disk/tape hybrids, tiered storage architectures and virtual tape.

Management Tools

Emerging library management software improves diagnostics, alerts, threshold requirements and drive/media management. Advanced Digital Information Corporation (ADIC) and Quantum, for example, have recently introduced native management software tools on their tape libraries and drives. ADIC's Scalar i2000 can alert administrators to potential problems, partition itself into logical libraries and carry out sophisticated self-diagnostics. Quantum's DLTSage, which it introduced last summer and is still pushing hard, runs proactive diagnostics like critical threshold alerts and error condition warnings.

Disk/Tape Hybrids

One of the more interesting developments is a tape library with a disk front-end. In this model, data writes quickly into the front-end disk cache and later writes to the back-end tape pool without impacting applications or backup performance. Policies control the migration to tape: data that is being migrated to long-term archives might pass immediately through the disk cache, while backed-up active data might stay in cache for some time, allowing fast recovery. (Common time periods are a week for daily file backups to 6 months for database data.) The library management software may be the source of the migration policies, or it may work with third-party HSM tools (Hierarchical Software Management).