RAID breathes new life into SSD
By Zachary Shess
The continuing emergence of RAID has helped breathe new life into solid-state disks (SSD), a technology first developed in the 1960s and once considered far too expensive for most computing environments.
A recent report from Peripheral Research Corp., a consulting and market research firm in Santa Barbara, CA, forecasts increased use of SSD over the next few years. In 1990, SSD sales revenues totaled $31 million. By 1997, revenues increased to $72 million, and they are expected to top $120 million by the end of 2000. In 1990, total SSD capacity shipped was 155GB, and it`s expected to reach nearly 16TB in 2000.
SSD suppliers include BGI Datentechnik, Database Excelleration Systems (DES), Imperial Technology, M-Systems, and market leader Quantum.
SSD technology dates back to the 1960s when it was a rackmount format used in scientific, military, and telephone exchange applications. It was not until the 1980s that SSD could be inserted and used like a standard magnetic disk drive. While analysts have stopped short of characterizing the current resurgence as a renaissance, SSD`s growth can be directly tied to its lower cost and increased use in RAID arrays.
"With the lower costs, utilizing solid-state disks makes sense now because they finally fit into the price equation," says Dennis Waid, president of Peripheral Research.
RAID is rapidly becoming de rigueur in high-performance storage and data access applications. But the performance of even the most expensive arrays falls short in very I/O-intensive applications. As a result, many RAID suppliers are starting to add SSD to their arrays in an effort to enhance performance and differentiate their products in an increasingly "me too" market. Because SSD is dedicated semiconductor memory with near instantaneous access times, these augmented RAID devices with accelerated data retrieval ability are now regularly used in mission-critical applications such as online transaction processing, Internet, video/graphics, CAD/CAM, databases, and decision support.
RAID vendors that have incorporated SSD into their arrays include Amdahl, Digital, ECCS, EMC, Hewlett-Packard, IBM, MTI, Siemens, Storage Computer, Seek Systems, Tandem, and Zitel.
The performance boost from adding SSD to a RAID configuration varies widely, depending on a number of factors, but on average it can significantly decrease average response times (see chart). Sybase recently performed detailed tests evaluating the performance increases possible with SSD. The tests were performed with MTI`s Database Accelerator in both Unix and NT environments. Complete test results are available at www.mti.com/freeinfo.
SSD was once relegated only to high-end applications. However, according to the Peripheral Research study, vendors today are providing SSD with capacities and price points that better fit into midrange environments. Using SSD to accelerate database performance is currently viewed as the predominant midrange application.
However, SSD memory costs remain fairly prohibitive, and its use is still not widespread. In 1990, SSD cost about $200 per MB, as opposed to $6.86 for standard disk drives. In 1998, the price differential is $20 per MB for the least expensive SSD vs. $.068 per MB for standard disk drives.
In fact, with SSD costs remaining fairly high, Waid believes SSD is still too expensive to be utilized much beyond specialized, high-performance RAID applications. In addition, because SSD is designed to emulate disk drives in RAID configurations, SSD performance has been hamstrung by the SCSI interface. However, with the emergence of Ultra SCSI, Fibre Channel, and IBM`s Serial Storage Architecture (SSA), SSD`s bandwidth will become more fully utilized.