SANs Are Here – Technology Information
Storage Area Networks (SANs) are here. They’re widely discussed and they’re in demand. Storage performance and storage space dilemmas are all too common for sites running memory “killer” applications like imaging, transaction processing, multimedia, data warehousing, and Internet downloads. And, as networks continue to expand and applications have to chum more and more data, increasing amounts of high performance storage subsystems are needed to keep pace. SAN solutions address these rapidly growing storage needs.
As processor and application performance have increased exponentially over the last decade, Unix and Windows NT distributed platforms have largely replaced data center-centric computing models. But during this same time span, improvements in file access and data transfer techniques have been minimal; now they have reached the critical point where server-to-storage communications have become the major roadblock to improved systems availability and performance. Today, SAN technology is changing this; it is deploying mainframe-class host-to-storage functionality to the enterprise network environment at open systems price-points.
A SAN is a dedicated network-type communications link between multiple servers and storage device(s). Its high bandwidth and high availability provide improved server-to-storage efficiency and through-put while freeing the LAN from the large packet data transfer chores and the bandwidth intensive overhead associated with storage tasks. The removing of storage-access functions provides a big boost to overall network performance.
How It Is
In the traditional approach, a storage device (e.g., disk, tape, RAID) is typically attached to an individual host (server) via a point-to-point connection such as a SCSI bus. With this one-to-one structure, each server utilizes its own unique data management architecture, segregating storage management tasks and making centralized control nearly impossible in an open systems environment. In fact, with this approach, when a site requires additional storage capacity, MIS administrators often turn to off-line expansion on each individual server as the “safest” and simplest solution. Additionally, in this setup, file accesses and data transfers between storage devices must travel the busy LAN pipeline, straining bandwidth resources and resulting in sluggish response times across the network.
Overall LAN degradation caused by extensive server-to-storage communications over the network is common and is not easily remedied in present SCSI-bus configurations. Due to restrictions in cable lengths, bandwidth, and connectivity, MIS Administrators are hard pressed to break this data traffic logjam.
How It’s Going To Be
1999 is the year SANs are crossing the chasm between early adopters and general market acceptance. Two years ago, less than 10% of IT administrators in a distributed LAN environment understood storage area networks. Today, SAN stories fill the cover page and storage sections of most IT publications and SAN benefits are being discussed at all major industry events.
As SANs are integrated into existing enterprise networks, users gain faster access to gigabytes of data, a higher level of data availability (rivaling that afforded mainframe files), and a more reliable, fault-resilient server-to-storage device hardware path than was possible previously. Most early SAN deployments concentrated on enhancing storage-to-network data transfers by replacing SCSI-buses with Fibre Channel I/O paths for communications with disk storage devices. These installations received the immediate benefits of increased bandwidth (100MB) for faster file throughput over longer distances (10KM) than was possible with SCSI-buses (80MB and 25 meters, respectively). Today, new software is enabling additional SAN benefits like remote tape vaulting and disk mirroring, backup/ restores with dynamic tape drive allocation, and high availability clustering. In the future, SANs will turn storage into an enterprise-wide commodity that can be allocated to applications when and where needed.
Peter Tarrant is the vice president of marketing at Brocade Communications, Inc. (San Jose, CA).
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