The UltraSCSI Buzz
Commandos and Cosbys
Today’s large number of computer system manufacturers and component suppliers has led to an interesting contrast of harmony and high performance. Individual companies are able to design and manufacture products developed to work in complete harmony with other peripherals and applications on a system. A symbiotic relationship grows as applications learn to co-exist with one another, share information, and not terminate each other. The relationship, in a way, is like a family on the go: the siblings keep themselves separated by an imaginary dividing line down the middle of the back seat of the car, while parents facilitate harmony and the best behavior of the children. The family, however, would not necessarily be seen as a first choice to act as a crack commando team working at full efficiency and interoperability on a critical mission. Instead, the concept of a family leans more towards one where harmony and mutual enjoyment of one another is a chief concern.
Today, many computers, distinguished by potentially blazing operating speeds and efficiency, are run more like a family than an elite commando team. Applications are taught not to hog system resources and overwrite each other’s files. A disquieting peace seems to exist between peripherals, like a motherboard and fax/modem, with situations of détente existing momentarily. The operating system and motherboard act like a mother and father. They maintain an order between the wide array of devices and programs constituting the family known as the "computer." All too often, this arrangement leads to a state of mediocrity where mere co-existence and momentary acceptance of one another--is all that could be expected, and is thus accepted.
While these issues may not seem too important to the computer user whose system is used mostly for balancing the checkbook or writing a "thank you letter" to Aunt Sue, high performance applications cannot accept mediocrity. Web servers today are averaging as high as 57 hits each second while audio/video (A/V) applications are streaming from hundreds to over a thousand megabytes of data each minute. These examples, along with many other real-life applications, demand peak hardware performance 24 hours a day, seven days a week. All hardware and software must work decisively as a team to accomplish mission-critical tasks rapidly and reliably, rather than merely co-existing with each other.
While there is no "miracle" cure for tuning and optimizing today’s and tomorrow’s systems to transform them from being simply workers into peak performers, there are steps that can now be taken to begin the process. One such step is the UltraSCSI interface, a bridge between the new, prominent line of high-performance disc drives entering the market today and the motherboard/processor/network, whose speeds are also increasing at a seemingly parabolic rate.
The Bottleneck Shifts
Traditionally, single user applications, and even some client/server environments, have seen throughput performance at a peak at the processor, slowing down throughout the system’s channels and buses, and slowest at the peripherals. Many of today’s applications are focused more on the manipulation and transfer of data than on the traditional role of simply "crunching numbers" for hours on end. For example, the mainframe, which used to ponder solutions to equations for long amounts of time, has been replaced by the PC server which handles a company’s transfer of e-mail and data files. Thus, the focus on performance has also shifted, and a stronger emphasis on the channel, not the processor, has become necessary.
With this increased demand for data and its transfer, so has the need increased for data storage. Now, SCSI interfaces accommodate several, if not dozens, of disc drives, tape drives, and other devices used to contain data needed in an online or near-online format. As each device is added to the SCSI interface, so does the amount of potential bandwidth used on the channel increase incrementally. With enough devices performing fast enough, the amount of available bandwidth can be quickly used up and, as a result, the system will soon find its bottleneck not at the traditional peripheral level, but instead now at the interface level. To better understand the need for extra bandwidth, imagine a road 20 feet wide. The road is unconventional in that no lanes are painted to separate the vehicles, but the one rule is that no more than sixteen vehicles can travel abreast at any one time. Two or three cars, five feet wide each, find no difficulty traveling down the road next to each other--enough space exists between them and there’s room to spare. A motorcycle, just one foot wide, can even drive alongside in a relatively comfortable manner. Problems arise, however, when a fast-moving big rig starts rumbling down the road, measuring a whopping 10 feet across, causing each vehicle to vie for its own space on the road.
This example is, in effect, the Wide Fast SCSI-2 environment. The Wide Fast SCSI-2 interface is capable of handling data at a rate of 20 Mbytes/second. This rate was quite acceptable up until recently, where perhaps a few high-performance disc drives would act as the automobiles and some other devices, such as a scanner, would represent the motorcycle. But as technology progresses, this situation can become problematic. For example, Seagate’s new Barracuda 9 and Barracuda 4LP disc drives transfer data at up to 12 Mbytes/second, roughly the equivalent of the big rig in the earlier illustration. Ironically, if the Barracuda 9 or Barracuda 4LP were attached to a conventional Narrow Fast SCSI-2 interface that only supports 10 Mbytes/second, the drive would not be able to achieve its full performance potential in the system!
Widen the Road and Watch Traffic Pick Up
UltraSCSI effectively eases the strain on data throughput by taking what would be a four-lane road and turning it into an 8-lane highway. The interface doubles the data transfer rate over both the narrow and wide versions of Fast SCSI-2. Entirely SCSI-3 compliant, UltraSCSI is backward compatible with earlier SCSI interfaces, including Fast SCSI-2, while effectively broadening the road in the earlier example from 20 feet to 40 feet in width.
UltraSCSI is especially attractive to legacy systems where low-cost upgrades are key, while the current system topology should be maintained and compatibility to existing system hardware is critical. UltraSCSI hits the mark in all three of these categories. The cost delta between Fast SCSI-2 and UltraSCSI peripherals and devices varies depending on the manufacturer and product, but it is nominal at worst and non-existent at best. Since UltraSCSI provides backwards compatibility, replacing hardware without major changes to system structure is feasible. Further, UltraSCSI is simply the next generation of the Fast SCSI-2 specification, and the tradition of maintaining backward compatibility to older peripherals and devices is maintained. For instance, an UltraSCSI controller can replace a Fast SCSI-2 controller at any time, unbeknownst to the attached peripherals, and the Fast SCSI-2 protocol will be maintained perfectly.
Under the new standard, Narrow UltraSCSI provides 20 Mbyte/second interface performance, up from the earlier 10 Mbyte/second ceiling. Wide UltraSCSI, as mentioned earlier, rivals the performance of some low-end serial interfaces by boosting the 20 Mbyte/second standard to 40 Mbytes/second. Both Narrow and Wide UltraSCSI support the pin configurations of their preceding interfaces, so no new connectors are necessary. Depending on the quality of the existing cabling and how well it meets and/or exceeds the requirements for UltraSCSI cabling, very little, if any, replacement cabling may be needed.
New Power, New Possibilities
UltraSCSI is true to its promise of acting as an enabling technology. No parallel interface before has offered data throughput as high as 40 Mbytes/second, and only Fibre Channel-Arbitrated Loop (FC-AL) can currently deliver higher performance from a serial interface. UltraSCSI is an ideal solution for users who maintain a system of a half dozen to several dozen disc drives and are feeling the pinch of needed bandwidth but are not in a position to migrate to the FC-AL serial interface. UltraSCSI delivers proven performance, interoperability, and backward compatibility today with disc drives, interface cards, adapters, cabling, and other peripherals offered by dozens of companies, often with immediate availability. Applications ideally suited for UltraSCSI are those that require such a high sustained data transfer rate. These include the growing medical imaging market, where huge graphical images and scans are transported from system to system, as well as internet applications, where millions of hits are being registered on servers daily. Even the more conventional office environment benefits from UltraSCSI. As client/server computing continues to replace the mainframe and communications between local area networks (LANs) and wide area networks (WANs) increases, the demand to share vast amounts of information rapidly increases and performance becomes increasingly critical.
Seagate is Ready, Set, and Going
Seagate has built a reputation in the data storage industry for pioneering advanced storage technologies in mass-produced products. Historically, this includes the implementation of the first micro-Winchester drive for PC’s, the first 5,400-rpm disc drive, and the first 7,200-rpm disc drive, as well as the development of the ST-506 (MFM) interface. Today, this tradition extends with Seagate’s introducing the first 9- and 23-Gbyte disc drives, as well as the first to begin mass production and distribution of UltraSCSI disc drives with the Hawk 2XL family. Introduced in volume this past March, the 5,400-rpm Hawk disc drives deliver 1- and 2-Gbyte capacity points ideal for various server and workstation applications.
Later this year, the award-winning Barracuda family will offer the latest in the series of disc drives to enter mass production with an UltraSCSI interface, as well as Seagate’s capacity monster--the Elite 23 disc drive. Great care has been taken at Seagate and various interface, chipset, and cable manufacturers to maintain compatibility and inter-operability between Seagate UltraSCSI disc drives and other UltraSCSI products. Other disc drive manufacturers share Seagate’s enthusiasm for the UltraSCSI standard and are also developing storage products that utilize the UltraSCSI interface.
Catch the UltraSCSI Buzz
Although UltraSCSI is not a technology that directly affects the internal performance of a disc drive, it is a key enabling technology to the overall performance of disc drives and systems. Just like a car will always accelerate faster, corner better, and get much more bang for the gallon when driving on concrete as opposed, say, to sand, high-performance disc drives, like Seagate’s new Hawk, Barracuda and Elite models will also achieve their true capabilities as a result of this advanced interface technology. And with that in hand, high performance systems can further improve their capabilities as the "crack commando teams" of computing.
By Tyson Heyn - July, 1996