Trends In RAID Technology.

Charting the future helps users pick the best RAID-based storage solution

Today's technology is continually advancing, particularly in the field of storage and RAID (Redundant Array of Independent Disks) solutions. Developers constantly create new, more advanced ways of managing and controlling information. RAID, a way of storing the same data in different places redundantly on multiple hard disks, has become a necessity. The amount of information and data being stored on hard drives has increased exponentially, along with the need to keep that data accessible. And, the need to have constant access to the data with the ability to update it grows daily. With that need in mind, manufacturers have developed and provided various different solutions to the ever-expanding market. RAID solutions can be used for any need and any level, from desktops and workstations to enterprise servers.

Developed by UC Berkeley's computer science department 20 years ago, RAID became a much-needed source of storing data due to the changes in technology and the use of computers. Computers and hard disk drives became faster, smaller and cheaper. The computer became a critical part of an organization's business. More and more data was stored in the computer and this information needed to be available 24/7.

In 1999, host-based RAID units grew 39.8 percent from 1998, which was twice that of multi-user server platform units, and UDMA or IDE RAID cards grew 167 percent from the previous year. Several challenges surfaced in the storage industry, including the need to:

* Improve system I/O performance at the pace of computing performance increases so that access to data did not become a limiting factor for applications; and;

* Provide uninterrupted access to on-line data at levels of reliability in excess of the expected lifetimes of the computer systems that process it.

* Why RAID has become a popular solution:

* The primary server bottleneck continues to be I/O Power, not CPU.

* The Internet industry's continued success depends on I/O throughput (LAN and Disk).

* PC servers are growing into mainframes and minis -- they need to match the I/O.

* The dollar per MB of storage continues to rapidly decline.

As we all know, data accessibility and reliability are essential key factors in today's business world. With more accessible and reliable data comes a price. How much of a price? It depends on the total storage requirement, the type of redundancy, and how quickly users need to recover from a failure. The cost of this hardware should be measured against the cost of system failure and the cost of downtime due to this failure. Some industries can sustain the loss of a disk drive or two and not suffer financially. Others where 24/7 availability is a requirement, such as brokerages, measure revenue loss in minutes of downtime. For this class of customer, RAID with full redundancy is a must-have.

One growing trend in RAID is Ultra l60 SCSI PCI low profile RAID controllers. Low profile PCI is a new PCI card standard for space-constrained system designs that maintain the same PC signals, electronics, functionality, and software drivers as standard PCI expansion cards. Based on the Low Profile PCI Standard (LPPCI) developed by the PCI Special Interest Group (SIG), the low profile RAID controller, targeted for 1 U and 2U servers, allows information technology (IT) managers to save expensive rack space, reduce co-location costs, and increase the available space for RAID storage, routers, and other types of adapters.

In addition to enabling these small rackable servers, the low profile board delivers increased value to workstations and dedicated task servers that have little space for add-in options. The low profile form factor 'meets customers' need for a physically smaller server. Until now, server OEMs desiring optional 110 configurations on their low profile rackable servers needed to mount standard PCI adapters horizontally. In many cases this increased overall implementation costs, limited flexibility, and hampered the ability to provide increased system scalability.

Choosing the best approach to RAID-based storage requires application and requirement analysis, and today's end users and systems integrators are faced with a steadily increasing number of technology choices. Fibre Channel is slowly taking a larger share of the high-end market from SCSI, while less complex and less expensive host-based RAID systems are becoming increasingly attractive to low-end and mid-range users. While new bus technologies continue to improve open storage bottlenecks in speed and other limitations including, cable distance, drive capacity and capabilities, drive prices continue to drop steadily. Some of the latest bus and interconnect standards that are driving the storage industry include:

Ultral60. A subset of the Ultra3 SCSI standard, it allows a maximum throughput of 160 MB/sec. which is more than twice as fast as Wide Ultra2 SCSI. Ultra3 SCSI has six new features in its specification, including Double Transition Clocking (DTC), Cyclic Redundancy Check (CRC), Domain Validation, Protection for Asynchronous Information Phase (AIP), Packetization, and Quick Arbitration and Selection (QAS). Ultra3 SCSI products can include any of the above mentioned features. Keep in mind, however, that just because a product says it provides support for Ultra3 does not mean that the product supports all the features listed. Most industry leaders: in. SCSI peripherals and SCSI processors have agreed to support a common denominator feature set which includes all the Ultra3 SCSI features except AIP (Fairness), Packetization, and QAS.

Fibre. A highly reliable gigabit interconnect technology, it allows concurrent communications among workstations, mainframes, servers, data storage systems, and other peripherals using SCSI and IP protocols. It delivers a new level of reliability and throughput. It is the best solution For IT specialists who require reliable information storage and delivery at blazing speeds.

Ultra 320 SCSI. The latest iteration of the SCSI drive interface standard, it enables maximum data transfer rates of up to 320MB/sec per channel, which is twice as fast as the Ultral60 standard. It also adds packetized commands which will make command overhead comparable to fibre, thus further reducing the gap.

PCI-X. An open standard that can be adapted and used by all computer developers and doubles the speed and amount of data exchanged between the computer processor and peripheral. PCI-X enables one 64-bit bus to run at 133MHz, with the rest running at 66MHz, providing, a data exchange rate of 1.06GB/sec. PCI-X is backward-compatible; the user can install a PCIX card in a standard PCI slot and receive a decrease in speed to 33MHz.

PCI-X should make its first appearance as a viable and acceptable technology in 2001 with implementation coming from the general release of Intel's 64-bit Itanium processor, which addresses the requirements of high-end servers and workstations for new levels of performance, scalability, availability, and serviceability for high-end applications, such as e-commerce, online transaction processing, and business intelligence.

InfiniBand. A new bus standard in the server market that has transfer speeds at 2.5Gb/sec of full duplex. Unlike PCI-X, InfiniBand will support devices located both inside and outside the server or storage system. Its switched fabric architecture will provide a common foundation with flexibility, scalability, serviceability, reliability, and performance for server cluster communication, networking, and storage.

SCSI over IP. It enables existing Fibre Channel and SCSI storage infrastructures to be connected to storage networks using Internet Protocol (IP). It will enable IT organizations to build storage area networks (SANs) based on IP networks such as Gigabit Ethernet.

IDE RAID. One of the fastest growing segments of RAID technology is ATA, an abbreviation for AT-Attached, also known as IDE (Integrated Drive Electronics). Though many users in the industry were: skeptical of IDE RAID's performance when introduced, it became an acceptable standard in the industry as IDE drives got faster and more people bought into the idea of having an IDE RAID controller as a cheap alternative. In 1999, GartnerGroup Dataquest stated that ATA RAID gained a definite share of the overall host-based RAID controller market.

IDE RAID is a viable, cost-effective solution for desktops, workstations, and entry-level servers. Once viewed as strictly a desktop or mobile play, Ultra ATA/100 has made great strides in traditional high-end SCSI markets. Problems with performance, capacity, and scalability have been eliminated. As a result, analysts expect ATA to penetrate entry-level server, RAID, and network-attached storage (NAS) segments.

IDE RAID is needed anywhere a low-cost solution is desired that provides high performance and data protection. The proliferation of new startup companies in fields such as 3D graphics, CAD Design; digital video editing, and desktop publishing has created a need for inexpensive, high performance, data security desktops and workstations. For users, the appeal of building huge storage capacities with super-fast data access and retrieval is essential. Users can build storage capacities with multiple drives to create "virtual" drives that haven't been born yet.

Nowhere is there a bigger current and potential market for IDE RAID than environments where data is critical: from professional services like accounting, medical offices, legal, and insurance to small offices with entry-level local area networks. Retail store operations, restaurants, and convenience stores record transactions for data processing. All of these environments depend on having data available 24/7 and protected. The same professional user can have IDE RAID data redundancy, inexpensively. If one drive crashes, it's the most cost-efficient insurance to data loss. An identical working drive keeps operating as if nothing happened.

IDE RAID supports the standard [network functions of data redundancy. IDE: RAID 1 (with two or more drives) and IDE RAID 5 (with three or more drives) permits a failed drive to be pulled out of the PC enclosure and a new drive swapped for it without stopping the system. This is critical for networks where continuous operation is critical. With either two arrayed drives or three arrayed drives (RAID 5 only), users can designate a standby drive to become active should the drive fail. The controller automatically turns to this drive and begins sending rebuilt data to it. Perhaps the biggest difference between conventional SCSI RAID technology and IDE RAID is the ease of installation. IDE drives have intelligence built-in and require no bus arbitration and no device termination to work properly.

Hardware-based IDE RAID is rapidly expanding into the NAS market as well. A unique and innovative way to add storage to a corporate or home network, NAS is the most intelligent personality in the storage industry. Developed as a low-cost storage alternative to traditional server environments, NAS solutions benefit from the enhanced performance and fault tolerant features of hardware RAID and the low cost of IDE hard drives.

Though ATA RAID continues to be selected as a viable alternative to more expensive SCSI-based systems for entry-level servers and performance workstations requiring the enhanced performance or data integrity of a RAID system, the ATA community plans to halt the ATA bus at Ultra-100 and migrate to Serial ATA (SATA) for all future generations. SATA, an emerging standard aimed at providing a high-speed, point-to-point, inexpensive serial interface between motherboards, hard disk drives, and CD/DVDs, has been adopted by all of the major disk drive companies and will be in use in 2001. Given the trends in the marketplace, it becomes clear that IDE is going to be around for years to come. With new technologies on the horizon for IDE, including SATA, the industry will continue to see new advancements in this technology.

Data storage and security will continue to be one of the most important technologies to the growth of businesses. RAID solutions will enable these businesses to continue to manage and control their important information. As more types of storage solutions are developed, the industry will provide these businesses with greater data reliability and accessibility.

Jim Evans is the storage marketing manager at American Megatrends Inc., (Norcross, GA).