Tape to take advantage of Fibre Channel

Posted on March 01, 1999

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Tape to take advantage of Fibre Channel

To keep pace with rapid technological advancements in network storage, manufacturers of tape drives and libraries are turning to Fibre Channel for answers.

Wes Kuch

Until recently, the industry focus on Fibre Channel, network-attached storage (NAS), and storage area networks (SANs) has primarily centered on disk subsystems, network connectivity, software, and servers. Computer tape drives and automated tape libraries have been thought of as SCSI-attached devices, if at all. The rapidly changing technological landscape necessitates a closer look at tape backup, Fibre Channel, and networked storage.

The combination of Fibre Channel and SANs not only enables real-time sharing of data among heterogeneous workstations, but also dramatically affects the efficiency of video production, post-production, and animation applications. Fibre Channel is also essential to the effective operation of specific NAS applications.

However, the ability to share data among servers, disk subsystems, and tape subsystems does not eliminate the old disk-to-tape or server-to-tape bottleneck issue. While faster Fibre Channel-based networks seem to solve the bottleneck problem, they require tape systems to perform at an equally high level. Current tape systems simply cannot achieve the throughput required for effective SAN or NAS environments.

This year, manufacturers will begin shipping direct-attached Fibre Channel tape drives with sustained data throughputs of up to 24MBps. Since Fibre Channel supports a much higher throughput than traditional SCSI interfaces (up to 800Mbps), the SAN I/O bottleneck is eliminated.

Why Fibre Channel tape drives?

Tape drives and robotic libraries typically use SCSI interfaces for data connection, which requires little, if any, drive intelligence. When tape back up is incorporated into a SAN, SCSI-to-Fibre Channel bridges are used to connect the drives and libraries, while a data mover (i.e., a data server or an OintelligentO disk subsystem) manages and distributes the data through the bridge. The data mover is yet another bottleneck between tape and the network.

But aren?t SANs suppose to eliminate the barriers of information availability and performance imposed by typical client server networks? Yes, if direct Fibre Channel interfacing is used.

Another advantage of Fibre Channel tape drives is its open-architecture for standard protocols (SCSI, TCP/IP, and video). This approach enables multiple applications (e.g., high-performance backup, SAP, digital asset management, and medical imaging) to reside on the same SAN. The implication: IT managers may be able to justify the costs of high-performance backup by incorporating a SAN.

In fact, Fibre Channel benefits tape subsystems in a variety of other ways:

- Higher performance for tape backup and retrieval

- Greater cabling distances, up to 10km

- Scalable performance with multiple protocols

- Reduced CPU activity for managing backups

- Enhanced monitoring and remote maintenance capabilities

- Lower overall operating costs

- Increased device connectivity, up to 126 per loop (more with public fabric)

- The ability to hot-swap tape drives

As SANs grow, IT managers will face new stresses. Data-intensive applications like digital asset management, IT asset management, digital studios, and on-line web applications will further test networks. The challenge will be managing direct disk-to-tape backup and integrating the data mover in these new environments. And then, there are the ongoing issues of data access, fault isolation, remote monitoring, and scalability.

Several key upcoming tape drive features address these issues:

- Higher effective data transfer rates. First-generation Fibre Channel tape drives will provide increased sustained data rates, which should provide enough bandwidth for most initial SAN applications. During the second phase of SAN development, new applications will evolve and greater amounts of data will need to be managed. Second-generation Fibre Channel tape drives will enable applications like high-definition digital video to be played back at real-time rates.

- Faster file access times. One of the key concerns behind tape is its relatively slow access time. As tape capacities increase, these times become more critical and will be unacceptable in Fibre Channel and SAN environments. For tape drive manufacturers, this issue is perhaps most difficult.

One potential solution is to use static RAM chips in the media to manage the files and directories, which enable the drive to retrieve files much faster than previous generations of tape drives. With the future development of larger and faster ICs, manufacturers may be able to insert more information into the chip, thereby improving file access times and enabling manufacturers to place pertinent information about the media inside the chip. This information may include error counts, the number of media loads and date stamps.

- Intelligent tape drives. It is also possible to build intelligence into drives by adding processing power. Internal CPUs will enable drives to manage themselves and communicate on the storage area network. These intelligent drives will be able to perform various routines (such as cleaning and maintenance operations, advanced performance diagnostics, and automated tape mirroring for disaster recovery) without the intervention of the host or network software.

The IT market is driving some of these developments, as is broadcast/video. Regardless of the applications, the advancements in Fibre Channel and SANs will play a key role in the development of tape drives for the next several years.

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