TAPE AUTOMATION AND THE MIGRATION FROM SCSI TO FIBRE CHANNEL.The need to backup and restore mission critical data throughout the enterprise has led to improvements in tape technology and storage automation. SCSI SCSI in full Small Computer System Interface Once common standard for connecting peripheral devices (disks, modems, printers, etc.) to small and medium-sized computers. SCSI has given way to faster standards, such as Firewire and USB. has been the backbone to interconnect (1) To attach one device to another. (2) A physical port (plug, socket) or wireless port (transmitter, receiver) used to attach one device to another. servers and tape libraries. Systems and network administrators have expressed the requirement to improve storage management control, share tape automation resources among multiple servers, and achieve improved performance. There has been a historical migration from SCSI to Fibre Channel implementations for RAID subsystems and this same migration is now occurring with tape automation. The steps include using bridges/routers, then Fibre Channel controllers, and finally Fibre Channel-enabled drives within the tape automation subsystems. HISTORY Tape automation first became popular in the mainframe environment as a means to control tape mounting operations for large numbers of sequential files. Within the open systems environment, tape libraries appeared to automate the backup process by eliminating operator intervention and the resulting errors of manual handling. With SCSI as the dominant interface in the open systems environment, tape libraries and the tape drives contained within the libraries used the SCSI interface SCSI interface - SCSI adaptor . Initially, a tape library was connected to a single server with backup software See backup program. (tool, software) backup software - Software for doing a backup, often included as part of the operating system. Backup software should provide ways to specify what files get backed up and to where. residing on that server. With the proliferation proliferation /pro·lif·er·a·tion/ (pro-lif?er-a´shun) the reproduction or multiplication of similar forms, especially of cells.prolif´erativeprolif´erous pro·lif·er·a·tion n. of distributed systems Distributed systems (computers) A distributed system consists of a collection of autonomous computers linked by a computer network and equipped with distributed system software. , IT installations began to have many servers, all with the need for automated backup. The choice was to put a tape library on every server, an expensive alternative, or to connect servers together across the network and utilize one or more servers to perform backup for the other servers. This contained the cost exposure of multiple tape libraries, but introduced the performance bottle neck associated with sending large amounts of backup data across a relatively slow network. The network would get congested con·gest·ed adj. Affected with or characterized by congestion. congested ENT adjective Referring to a boggy blood-filled tissue. See Nasal congestion. and the effective transfer rate to the tape drives would suffer because of the network speed. As the concept of the Storage Area Network (SAN) was accepted, the vision became multiple servers sharing a tape automation resource with high speed back end links from each of the servers to the tape library without having to send data across the front end network (LAN-less backup). Fibre Channel has emerged as the technology of choice for the high speed interconnect NVIDIA's High Speed Interconnect (often abbreviated to 'HSI') chip was used in their early PCI Express graphics cards, where it acted as a bridge between the PCI Express connection to the computer and the natively AGP GPU. . RAID BACKGROUND Before exploring the tape automation environment itself, let's look at how Fibre Channel implementations began with RAID systems. The easiest first step was to take an existing SCSI-based RAID system and hook it to Fibre Channel using a bridge/router. This required no new investment in the RAID system and the bridge/router would convert from the SCSI interface of the RAID system to the Fibre Channel interface of the interconnect infrastructure. The disadvantage was that the bridge/router was a fairly expensive add-on device. The next step was for new RAID controllers A disk controller card that supports one or more RAID configurations. Originally only for SCSI drives, RAID controllers have become very popular for PATA and SATA drives. See RAID. to be introduced that provided Fibre Channel interfaces. The controller could attach directly to the Fibre Channel infrastructure and, within the RAID subsystem A unit or device that is part of a larger system. For example, a disk subsystem is a part of a computer system. A bus is a part of the computer. A subsystem usually refers to hardware, but it may be used to describe software. , the controller could communicate with SCSI disk drives. The final step was to move to a full Fibre Channel implementation, whereby the RAID controller had a Fibre Channel interface to the outside Fibre Channel infrastructure and an internal interface to Fibre Channel disk drives. TAPE AUTOMATION Fibre channel implementations for tape automation are following this same three-step process that was followed by RAID subsystems. Today, the main approach being used is to connect an existing SCSI tape library to a Fibre Channel infrastructure using a bridge/router (Fig 1). Tape libraries have now come to market that have a Fibre Channel controller and can, consequently, connect directly to the Fibre Channel infrastructure (Fig 2).The final step will be an all Fibre Channel implementation, including a Fibre Channel library controller and Fibre Channel tape drives (Fig 3). Fibre Channel tape drives are just starting to appear and will become more prevalent over the next two years. REQUIREMENTS The need for Fibre Channel attachment of tape automation subsystems is being fueled by the growth of disk capacity and the resultant amount of information that needs to be backed up to tape. With more servers that have more disk space requiring timely backup of precious corporate information resources (1) The data and information assets of an organization, department or unit. See data administration. (2) Another name for the Information Systems (IS) or Information Technology (IT) department. See IT. , IT professionals face an increasing challenge to provide an effective backup solution. The specific requirements fall into three categories: storage management control, shared resources Sharing a peripheral device (disk, printer, etc.) among several users. For example, a file server and laser printer in a LAN are shared resources. Contrast with shared logic. , and performance. * Storage Management With a mainframe installation, storage management is centralized cen·tral·ize v. cen·tral·ized, cen·tral·iz·ing, cen·tral·iz·es v.tr. 1. To draw into or toward a center; consolidate. 2. . With distributed computing (1) The use of multiple computers networked throughout a wide geographical area, or the world via the Internet, in order to solve a single problem. See grid computing. (2) The use of multiple computers in an enterprise rather than one centralized system. , servers reside in multiple locations and the management of storage becomes more of a challenge. As the size of the network grows, the ability to effectively backup data, maintain a consistent storage management process, and protect the variety of storage resources becomes more of a problem. Some organizations have attempted to deal with this by recentralizing the servers, bringing the servers back into a common location. Others have attempted to recentralize the storage resource while still keeping the servers distributed. The main challenge is to provide central control of storage even if the processing and storage resources themselves are distributed. Fibre Channel offers the interconnect infrastructure that can facilitate improved storage management, connecting multiple servers and storage subsystems The part of a computer system that provides the storage. It includes the controller and disk drives. See storage system. across a campus environment. * Shared Resource As much as those of us in the tape automation business would like to sell a tape library for every server, this is not the cost-effective way to go. Tape libraries are an ideal shared resource for use across multiple servers. One IT executive shares this perspective, "One of the problems we have today with backup is most of the world considers that you backup one server at a time. You need some way to have multiple servers use a single tape library. A tape library is more expensive than a server. There is no way you can buy a tape library for each server." A complete Fibre Channel solution with appropriate software and switches/hubs can make this a reality. * Performance One of the challenges of a networked computing computing - computer environment is providing enough bandwidth to accommodate processes such as backup. Current networks aren't fast enough to support existing tape drives. As stated by one IT manager, "A lot of places are still on 10baseT for the backbone but everyone is moving to switched 100baseT or faster networks. That's a limitation in itself. The network is being used for things that it was never intended for." Another IT manager shares this perspective, "The interconnect to the storage is related, since if you use the network to interconnect between disparate servers, then the network becomes the bottleneck A lessening of throughput. It often refers to networks that are overloaded, which is caused by the inability of the hardware and transmission lines to support the traffic. It can also refer to a mismatch inside the computer where slower-speed peripheral buses and devices prevent the CPU ." A systems integrator adds, "The tape drives are faster than the network. We're looking at customers who can't do their backup at night because there isn't enough time. So they come in the morning to log in and have to wait for backup to complete." This problem will only be exacerbated with the improved performance of tape drives that are coming to market within the next year. A Fibre Channel SAN offers a pipe big enough to feed these tape backup Using magnetic tape for storing duplicate copies of hard disk files. Users can add an internal or external tape drive to their desktop computers for backup purposes, and files are typically copied to the tapes using a backup utility that updates on a periodic schedule. devices. When presented with a Fibre Channel solution at a focus group, an IT systems administration manager clearly summarized, "With this technology, I see some significant advantages with speed, particularly backing up. As a backup solution, it is much more attractive." SCSI has been the dominant technology to connect tape libraries to servers in open systems. With the emergence of Fibre Channel solutions, there exists an improved capability to address lingering lin·ger v. lin·gered, lin·ger·ing, lin·gers v.intr. 1. To be slow in leaving, especially out of reluctance; tarry. See Synonyms at stay1. 2. IT problems of storage management control, shared resources, and performance. Tape automation using bridges/routers is the initial approach being implemented. The next step includes Fibre Channel controllers in the tape libraries and, finally, there will be Fibre Channel capable tape drives in the libraries. Mike Befeler is the vice president of marketing and business development at Benchmark Tape Systems (Boulder, CO). |
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