Stay in touch…

Blog

Read the latest Bitstream

RSS Feed

LinkedIn

Look for us at LinkedIn

Twitter

Follow us on Twitter

Mix Magazine

This installment of The Bitstream column appeared in the May 2000 issue of Mix Magazine.

The Bitstream

This column discusses local and wide networks as well as storage area networks and network-attached storage…

LANs, WANs, SASs & SANs…or why networks are born anew

Was at a industry schmoozefest last night, meeting and greeting while munching on salmon thingies. Our small industry revolves around networking; knowing where to go to get what you need. That’s true in a more basic sense as well. If successful, a business expands from the one room of humble origins to multiroom facilities with phone lines bringing clients and talent in from far away. Most audio these days is numeric data and data loves company. So its no wonder that, whence cometh computers, networks aren’t far behind. Local and wide area networks (LANs & WANs) have evolved from relatively slow, expensive and ungainly implementations to current technologies that offer cost effective movement of bits at very satisfying speeds. Let’s take a look at some of the side paths on the road to SANs.

NETWORKS OF YORE

While sneakernet is still the "network" of choice due to budgetary constraint, trends in the IS industry have made true multiuser LAN–based production increasingly affordable. The first LAN product optimized for digital audio delivery was Sonic Solution’s MediaNet. First shipped in 1993, it enabled true multiuser availability of storage for the first time in our industry. Boasting more than 4500 seats at its peak, it leveraged the existing FDDI and CDDI standards. MediaNet employed a proprietary network file system and additions to the existing OSI reference model. These features provided bandwidth reservation for each node or user and guaranteed QoS (Quality Of Service), shorthand for guaranteed sustained throughput.

At the time, other vendors sold 10 or 100BaseT as an alternative but even with 100BaseT’s effective data rate of 12 MBps on a good day, the lack of multiuser access to a file and no QoS guarantees meant that such products are really only good for background file transfers. Another historical choice was SCSI switches. With SCSI’s infamous unreliability, I shudder to think of that technology as a long term solution.

Nowadays, sheer throughput compensates for lack of file locking or other seemingly essential file system features. ATM or Asynchronous Transfer Mode, a high speed cell–switching transport standard favored by WAN architects, is one LAN solution for audio wonks offered by vendors. Although ATM is capable of getting the job done, its high cost, inability to guarantee delivery, tiny fixed frame length and sizable transmission overhead means that its best used for what it was designed for; enterprise backbones and WANs.

Another choice for network transport is Ethernet. The recent replacement of stodgy old Ethernet with amazing new Ethernet, commonly known as Gigabit Ethernet, allows portions of existing wiring to be used in many instances. Though individual network interfaces, routers and switches need to be replaced, this technology is a sensible alternative to swapping an entire infrastructure, especially for background transfers.

THE NEW NETWORK MODELS

Like the softening of the boundary between professional and consumer, the distinction is blurring between local and remote, storage and interconnect, network and bus. A new chimera is increasingly being seen in critical production environments: a SAN or Storage Area Network. And SANs will transform the way new media producers work.

What happens when you attach your hard disks directly to a network interface instead of a networked server? You have NAS or Network–Attached Storage. NAS eliminates unreliable cables and termination, surely the weak spot in any SCSI installation. It also frees up server resources and can interoperate with multiple OSs and platforms. A good example of an inexpensive NAS appliance is Quantum.com’s Snap Server. Covering most small studio configurations, it supports Microsoft, Novell, Mac and UNIX NFS file systems. Just hang it off of a 10 or 100BaseT network et voilà, if a DHCP, BOOTP or RARP server is available, it autonegotiates an IP address assignment.

Unfortunately, NAS suffers from the same network bottlenecks that hobble traditional topologies: bandwidth limitations and the processing overhead required for packetizing and serializing the usually parallel SCSI data. Done well, NAS provides high performance, highly available, expandable storage. Done poorly, it simply delays the inevitable need to manage your storage budget, degrades network performance and greatly increases you administration costs. Consider the additional network traffic and administration costs that backing up a simple 40 GB NAS would entail. So, think of NAS as "starter" technology, easing the transition to SAN and interoperating comfortably with it.

SANs replace the traditional client/server and simple NAS models with a high availability, "storage-centric" local or remote network that directly connects storage, servers and clients. SANs are designed as networks dedicated to storage transactions, making that storage equally available to all users all the time at rated bandwidth. A separate, parallel messaging network, usually the existing primary network, carries other traffic like TELNET or those SNMP and HTTP transactions that we all know and love.

To give you some idea of how this fits into your microcosm, contemplate your average two or three room facility. The LAN would usually have 100BaseT connecting their DAWs, with all traffic flowing around that network. We assume that 16/44.1 stereo user traffic moves Segregating the storage on a SAN would remove all of the user traffic from the LAN and increase throughput by at least a factor of 10.

The current king of heteroconnections, Fibre Channel, is the most common choice for transport in SAN implementations. Its more than a network, its a way of life! Just kidding. Fibre Channel (FC) is a data management system, a unified approach to storage, network and control. It provides accessible supervision, scalable performance and versatile connectivity via simple point-to-point topologies with dedicated bandwidth or loops with shared bandwidth. For wicked fast connections with scalable bandwidth and greater reliability, switched connections are the way to go. They provide reliable QoS of over 1 Gbits/s with support for distances up to 10 km. Neither FireWire nor Ethernet supports QoS, end-to-end latency is an unknown variable with those delivery schemes. And that is potentially devastating for real–time network delivery of audio or video.

Another selling point is FC’s scalability. From point-to-point links at gigabit speeds to fabrics with multiple switches, FC delivers unmatched performance. Congestion free credit-based flow control delivers data as fast as the destination buffer is able to receive it. And, FC has very little transmission overhead.

Like it’s hermetic forbearer, the Chemical Wedding of Fibre Channel and cost effective WAN standards like xDSL promise to transform the soul of Squire SAN. What is usually a local storage network becomes as wide and far–reaching as your pockets are deep. Alas, we aren’t all Michael Eisner, but we may benefit from another disturbance in the storage force. With the recent introduction of FireWire–attached NAS, you can have some of the benefits of both NAS and SANs. Micronet.com’s groovy SANcube segregates the storage traffic on a plug and chug FireWire host bus and provides 30 MB/s availability for up to four simultaneous users. And, it’s got great LEDs to stare at when those guitar overdubs aren’t going so good. However, the administration burden would still be shouldered by an existing (Ethernet) LAN whereas a full blown SAN would provide both user access and backup via the Fibre Channel conduit. Remember, backup and management must be factored in to any Total Cost of Ownership equation.

Alas, though the old stuff works just fine, SAN and Fibre Channel are easing the burden of engineering and maintaining high performance production systems. Tight budgets being the norm, this technology will take a year or so to filter down to the average punter’s level. But, one must plan for tomorrow. So, in months to come, I’ll be looking at other advanced storage issues and future standards such as InfiniBand. If you’d like more information on SANs and Fiber Channel, drop by seneschal.net and check out the SAN links I’ve collected for you. For your part, crank up your mail client and let me know what occupies your thoughts…

Bio

Oliver Masciarotte is an engineer and new media consultant. He recently put to bed the first DVD-V release of 96/24 classical music, the Himalaya Sessions on Albany US.