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January 1999
RAID Today... and Tomorrow
Lowell Rapaport
RAID without controllers? What will they think of next? How about RAID as a component of storage networks and server clustering? Adjust your attitude to the new realities of RAID in document solutions.
If you ever had reservations about adding RAID storage to your system, either because you thought it would be too expensive or because it never seemed to deliver the promise of fast performance for your particular application, then there is good news. Hard drive storage is less expensive than ever, and new controller technologies let you tailor a RAID systemıs performance to suit your application and file sizes.
You may not even need a controller. Philip Black, president and CEO of Box Hill (New York, NY 212-989-4455) says that the low cost of hard drive storage makes controllerless RAID a reality. By controllerless RAID, Black means RAID Level 1 or mirroring. Mirroring can be accomplished entirely in software and requires only minimal CPU time. Mirroring also has advantages over the more traditional RAID 3 or 5. It offers more reliability than parity RAID since a complete duplicate of your data is kept on a spare drive. If a drive goes down, you donıt have to spend any time reconstructing your data.
The usual argument against mirroring, the high cost of maintaining duplicate drives, vanishes when you factor in the cost of redundant RAID controllers, power supplies and cooling systems. If youıre building a small RAID system (less than 100 megabytes), then it may be more cost effective to simply get dual SCSI host adapters and a JBOD (Just a Bunch Of Disks) array and use software to implement RAID 1-0.
Mirroring becomes expensive much faster than parity RAID as you add additional storage. To decide which approach you should use, you have to compare the cost of RAID controllers and single-array redundancy features against the cost of duplicate drives. At about 10 cents per megabyte, the current going rate for RAID-certified hard drives, a $10,000 RAID system is worth about 100 gigabytes of storage. When shopping for a RAID, figure how much disc storage you can buy for the cost of a RAID controller. If your storage requirements are less than the cost of a controller, then software mirroring is for you. If your requirements are more than the cost of a controller and redundancy systems, then a high-end RAID array will be more cost effective.
There is no shortage of high-end RAID arrays to choose from. A quick look at Imaging and Document Solutionsı Buyersı Guide (available online at www.imagingmagazine.mfi.com) shows dozens of companies ready to provide you with fully redundant RAID systems able to support terabytes of storage.
When buying a RAID system, redundancy is the primary goal. Itıs built into the RAID concept. How the redundancy is implemented is something you want to look at, however. There are many ways to do it.
The traditional method is to use a RAID system with an external controller. External controllers reside inside the RAID system enclosure. They are external from the serverıs point of view. Much of the latest activity in advancing RAID technology has been in making RAID systems equipped with their own controllers work on storage area networks (SAN) or as network attached storage.
Artecon (Carlsbad, CA 760-931-5500) recently introduced a new line of RAID systems, the LynxArray II ($10,000-$60,000). All versions of the LynxArray use external RAID controllers. The Series 200 and 300 use SCSI throughout and the Series 500 has a SAN-ready fibre channel controller.
External RAID controllers permit greater redundancy and fault tolerance than internal controllers. When paired up in an Active-Active configuration, performance is doubled as well.
Digi-data (Jessup, MD 301-498-0200) recently improved the performance of its Active-Active RAID controllers. Their latest product, the Z-9552 dual fibre channel RAID controller, has all the features found in modern RAID controllers: redundant controllers, dual fibre channel connectors, multiple SCSI channels for connecting hard drives, support for RAID 3 and RAID 5, upgradable cache, and software designed to detect and reconstruct data in case of a hard drive failure.
MTI (Anaheim, CA 714-970-0300 www.mti.com) Galdiator RAID systems range from $45,000 for a 72 GB entry-level system to hundreds of thousands of dollars for terabyte-sized fibre channel systems.
Asked about the high cost of entry-level RAID compared to the amount of storage, Gary Brenkman, MTIıs director of marketing, said about half the cost was for a fully redundant RAID controller. The rest was for certified 9.1 gigabyte drives. MTIıs mid- to high-end RAID systems are desinged to be put on storage area networks.
Storage area networks are an emerging technology for RAID. Enabled by fibre channel and combined with server clusters, the storage area network is the last word on redundancy, fault tolerance and centralized storage management. Since fibre channel and storage area networks are such a close fit, it's not surprising that most fibre-channel RAID vendors have storage area network strategies. Box Hillıs Fibre Box ($21,600 to $72,000) is pure fibre channel RAID. It uses software to combine striping and mirroring.
Xiotech (Eden Prairie, MN 612-828-5980) makes the Magnitude ($55,000 - $200,000), described by the companyıs president, Phil Soran, as a ıSAN in a box.ı The Magnitude series of RAID systems are designed from the get go to work with clustered servers and storage area networks. They include multiple server ports on each RAID system -- up to eight servers in some configurations. By the time this story sees print, Xiotech should have arbitrated loop, the network-like fibre channel connector, fully implemented. This will enable Magnitude series RAID systems to function on existing storage area networks with other storage devices.
Storage area networks are part of a larger industry trend toward peripherals that are not dependent on a server to function. In the last year or so there have been many storage devices that can be described as network attached. There have always been network attached printers and, more recently, network attached scanners. In the last year weıve also seen network attached jukeboxes and hard drives. It is not surprising that there are network attached RAID systems as well.
Network attached RAID shares the same advantages and disadvantages as other network attached devices. Administering a network attached RAID must always be done remotely, but can usually be accomplished from any computer with a recent Web browser. Network attached RAID will only function as fast as the network to which it is attached. If you have a database searching through files on the RAID, the database is limited to the speed of the network. Adding a network attached RAID only requires a free ethernet port and an IP address. You donıt have any SCSI or RAID controller cards to install and no server to reconfigure.
The Netforce 100 ($7,600 to $13,800) is one of the latest network attached RAID devices to come along from Procom (Irvine, CA 949-852-1000 ). A simple device from the system administratorıs point of view, the Netforce has a SCSI port for attaching a backup tape drive.
All the vendors mentioned thus far are planning or already offering fibre channel products. Some, like Box Hill, are very heavily into fibre. Others, like Digi-data, are making fibre channel RAID products as part of their broader product line.
But there are some companies prefer to make SCSI their first choice for deploying RAID systems. Adaptec (Milpitas, CA 408-945-8600), for example, has sold off most of their work on fibre channel technology to concentrate on SCSI. According to Adpatec, SCSI is going through a renaissance that will both simplify and speed up access to storage at the same time.
Ultra2 SCSI RAID controllers are just coming out now from companies like Adapatec, DPT, and Mylex. Ultra2 SCSI gives performance up to 80 megabytes per second. Adaptec is also planning ahead to Ultra3 SCSI (also referred to as 160M), which promises up to 160 MB/second throughput. On Adaptecıs roadmap are Ultra4 and Ultra5 SCSI, whose performance nobody knows. Easily available through retail channels, Adaptec RAID controllers are perfect choices for users who prefer to build their own RAID arrays.
One feature users can look for in the future is the ability to update a RAID system on the fly. When many users set up a RAID system for the first time, they typically get an entry level system that they quickly outgrow. Additional storage is always being added, even to an established system in a large enterprise. A RAID system that lets you add additional drives or change RAID levels on the fly without taking the system down is a definite plus in 24/7 environments.
DPT (Maitland, FL 407-830-5522) is among those designing RAID arrays that can be modified live. Robert Mohs, DPTıs technical marketing manager, describes the ability to upgrade RAID arrays on the fly as an extension of a feature most RAID systems already have--namely, the ability to hot swap drives and reconstruct data on the fly after a drive crash. DPT, which makes RAID controllers and subsystems, goes against the grain by making internal RAID controllers (that reside in the server rather than in the RAID array case) their primary business.
Mohs says, ıEach type of controller, internal or external has merits. External controllers are self contained and are great for companies that sell RAID systems. But you still have to buy a SCSI or Fibre host adapter for your server. By making internal [server based] RAID controllers, we eliminate a device the customer has to buy and make it possible for server manufacturers like Dell and Compaq to make RAID subsystems for their computers.ı
When asked if DPTıs internal controllers can support important redundancy features like Acitve-Active controllers Mohs said that they could, but the controllers have to mounted in separate servers in a clustering environment. U
Artecon
Carlsbad, CA 760-931-5500
What they make: SCSI and Fibre Channel RAID systems for servers and storage area networks)
Featured product: Lynxarray II, Server and Storage area network RAID
Capacity: 7 to 43 drives
Key points: Artecon has 3 series of Lynxarray II RAID systems. Series 200 has a single RAID controller, Series 300 and 500 have dual RAID controllers. Series 200 and 300 are SCSI RAID systems, Series 500 is fibre channel.
Price Range: $10,000 - $60,000 for complete RAID systems.
Box Hill
New York, NY 212-989-4455
What they make: SCSI and Fibre Channel RAID systems for servers and storage area networks
Featured product: The Fibre Box, a pure (both internal drives and external) fibre channel controllerless RAID system
Capacity: 73 gigabytes to 146 gigabytes
Key points: Box Hill is committed to fibre channel. The Fibre Box is one of the few all-fibre-channel RAID systems available (most others combine the two using an integrated fibre channel/SCSI bridge)
Price Range: $21,600 - $72,000
Digi-data
Jessup, MD 301-498-0200
What they make: SCSI and Fibre-channel RAID controllers for high-end systems.
Key points: Digi-data makes RAID controllers supporting RAID level 3 and RAID 3 and 5 with Ultra SCSI, Ultra2 SCSI and fibre channel connectivity. The Z-9552 is their top-of-the-line unit featuring RAID Level 3 and 5, fibre channel copnnectivity to host, and support for up to 90 hard drives on six ultra wide SCSI channels.
Price Range: Sold through OEMS only.
MTI
Anaheim, CA 714-970-0300
What they make: Server attached and storage network attached RAID systems, mid to high-end.
Featured products: Gladiator 3600 and Gladiator 6300
Capacity: Gladiator 3600 - 18.2 gigabytes to 1.3 terabytes. Gladiator 6300 - 17.7 gigabytes to 1.7 terabytes
Key points: Systems have fibre channel connections to the host computers.
Price Range: $45,000 and up for complete RAID systems, $21,000 to $22,000 for RAID sans drives.
Procom
Irvine, CA 949-852-1000
What they make: Network attached storage
Featured product: Netforce 100
Capacity: 20 gigabytes to 80 gigabytes
Key points: Procom also makes a Netforce 1000 with about ten times the capacity of the Netforce 100. The cost of a Netforce 1000 is roughly two to four times that of the Netforce 100
Price Range: $7,600 - $13,800 for network attached RAID
Xiotech
Eden Prairie, MN 612-828-5980
What they make: Server and storage area network attached RAID
Featured product: Magnitude Intelligent Disk Storage Subsystem
Capacity: 8 to 64 drives
Key points: The Magnitude can support multiple servers connected to a single RAID system. The rated transaction rate of 15,000 to 50,000 input/outputs per second is about ten times higher than many competing systems.
Price Range: $55,000 - $200,000
Adaptec
Milpitas, CA 408-945-8600
What they make: SCSI host adapters.
Key points: Adaptec is one of the most recognized names in the SCSI host adapter business and has led the way to Ultra2 SCSI. Adaptec also makes internal RAID controllers like the AAA-130SA SCSI RAID series. Adaptecıs cards are inexpensive and easily acquired through retail channels.
Mylex
Fremont, CA 510-796-6100
What they make: SCSI and Fibre-channel RAID controllers for high-end systems.
Price Range: $500 to $2,600.
Key points: After introducing fibre channel RAID controllers earlier this year, Mylex has been busy making Ultra2 controllers. Ultra2 features 80 megabytes per second throughput. Mylexıs line includes the Acceleraid 150 ($400) low cost internal controller and the DACFL ($2,000 - $4,000) fibre to Ultra2 SCAI bridge.
DPT
Maitland, FL 407-830-5522
What they make: Internal RAID controllers for servers and workstations.
Key points: DPTıs latest product, the Smart RAID V, is a modular RAID controller. The modular design gives DPT endless permutations on host bus interfaces (Ultra, Ultra2 and fibre channel), memory cache, number of channels, and controller processor speed. Whatever your application, DPT can fasion a RAID controller suited to it.
Price: $600 - $2,600
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