sdspThe computer industry continually rushes toward tomorrow’s great technological advance, leaving a wake strewn with yesterday’s hardware. Yet unlike operating-system developers, hardware vendors focus little on making their products backward-compatible.

The result: Chief financial officers wind up amortizing equipment over five years, even though it’s likely rendered extinct in two.

Bucking this trend toward accelerated obsolescence, Storage Dimensions Inc. released a high-capacity RAID (Redundant Arrays of Inexpensive Disks) subsystem with a twist. Not only does the LANStor SuperFlex system combine high reliability via dual-redundant power supplies, triple fans, and a sophisticated cableless SCSI backplane, it does so in a chassis that accepts disk modules from the company’s earliest ReFlex models.

With the hard drives’ mean time between failure exceeding 500,000 hours (more than 57 years), the SuperFlex offers investment protection that should help the bean counters rest easier. Although it is certainly not the least expensive RAID on the market, we were nonetheless most impressed by the SuperFlex’s performance, expandability, and myriad configuration possibilities. It also offers good protection when compared to Dell’s PowerEdge, which often needs data recovery (see this article).

First shipped last month, the LANStor SuperFlex chassis can house seven 3.5-inch drives that connect to the actively terminated SCSI backplane. The price for a complete seven-drive, 12G-byte system with EISA or PCI host adapter is $26,440. The system that PC Week Labs tested included Storage Dimensions’ $2,465 RAIDFlex I/O module, which is based on a Mylex Corp. DAC960 controller.

Storage Dimensions sells an empty SuperFlex cabinet for $3,125. Both Fast SCSI and Fast/Wide SCSI drives are available. Prices range from $1,470 for a 1G-byte drive to $4,900 for the high-end 4G-byte unit. Custom configurations and DDS-2 digital audiotape drives are available.

Performance

In our tests, we found the SuperFlex/RAIDFlex combination delivered excellent I/O performance. We expected this because the RAIDFlex’s Mylex-based controller has shown its mettle in previous testing.

What’s unique is that Storage Dimensions has incorporated the controller, which is usually used on EISA server adapters, into an I/O module that slides into the SuperFlex chassis. A user can start out with a basic SuperFlex system and upgrade to the higher-performing RAIDFlex when necessary.

This modular approach will also accommodate higher-speed I/O modules, such as Fibre Channel modules, when they become available. The RAIDFlex controller supports two SCSI channels and RAID Levels 0, 1, and 5, as well as Level 6, which is a combination of RAID 0 and 1.

Currently, Storage Dimensions offers drivers for NetWare and IBM’s AIX, but the company plans to release drivers for SunSoft Inc.’s SunOS, and Hewlett-Packard Co.’s HP/UX this quarter; drivers for Windows NT and OS/2 are due in January.

We installed the supplied BusLogic Inc. EISA controller in a Compaq Computer Corp. ProLiant 2000 equipped with 132M bytes of RAM and running NetWare 3.12. Using the RAIDFlex management program, we configured the system for RAID Level 5 using five drives, with a sixth drive defined as the hot spare.

We had the option of setting write-back or write-through for the RAIDFlex cache as well. Formatting the six drives — almost 10G bytes of disk space — took several hours. Once that was done, we used NetWare’s INSTALL NLM to define a volume on the array.

Testing the spare

Next we connected 16 NetBench clients to the RAID system and had them begin reading and writing to the volume. To simulate a failed drive, we pulled one of the disk modules from the SuperFlex. A slight pause of disk activity was followed by a prompt switch over to the spare drive. The clients experienced no glitches or hiccups because the SuperFlex drivers were able to suspend disk activity for this brief period.

When we replaced the drive, the system assigned it as the new hot spare. From the management screen, we could set the threshold of CPU utilization for rebuilding the array, but unlike other RAID systems, LANStor SuperFlex did not allow us to permanently set this attribute.

Storage Dimensions bundles a Lite version of its RedAlert notification package with SuperFlex. Running as NLMs on the server, the program can send out alerts via pager; MHS, VIM, or MAPI E-Mail; or a 25th-line NetWare message when things go awry in the RAID. However, we were disappointed to find that only drive-related failure conditions prompted RedAlert to send an alarm; a dead fan or power supply will not elicit any SOS. Storage Dimensions is working to enable the SuperFlex to trigger alerts for these c onditions as well.

We were pleasantly surprised by the clutter-free interior of the SuperFlex housing. Because of its SCSI-backplane design, it has almost no cables. In addition to making access much easier, the lack of cables enhances the system’s immunity to electrical noise.

By moving a pair of ribbon cable jumpers, we could split the backplane into two independent buses. The three fans mounted across the rear of the unit can be hot-swapped, as can the two power supplies, which feature separate cords.