Off-the-Rack RAID

Charles Lin

When it comes to backing up and storing data, we hold certain truths to be self evident: All data is created equal, and it needs to be stored. RAID (redundant array of inexpensive disks), which has been around for years, is one of the best storage solutions: It gives you the redundancy you need without mirroring each hard disk. For small businesses, however, the cost of RAID has been prohibitive, but not anymore. Adaptec, a major player in the SCSI controller market, has just introduced its PCI RAID controller, the AHA-3985, with a price tag of only $795.

With the release of this product, Adaptec has made its first foray into the RAID-controller market. And the debut has been remarkably strong. Aimed at server environments with less than 50 clients, the AHA-3985 is an affordable RAID controller. Currently, Adaptec sells a narrow SCSI version for $795 and a wide version (AHA 3985W) for $849. Also included with the controller is Adaptec CI/O RAID management software, HP OpenView, and a server-based NLM tape backup utility.

According to officials at Adaptec, they were able to offer the AHA-3985 adapter for such a low price by designing it around the PCI bus architecture. The ability to move data off-bus without much buffering on the adapter means that the AHA-3985 only requires one megabyte of expensive onboard DRAM. Each SCSI channel on the adapter is controlled by its own Adaptec 7170 chip.

Now for a little refresher on how RAID works. RAID combines multiple disks in an array that appears as a single disk to the operating system. Using parity information, RAID offers data redundancy to multiple disks while sacrificing only a single disk's worth of storage.

RAID Level 5 adds even more functionality by distributing the parity information evenly across the array, thus allowing any disk to fail without disrupting services to the clients. For a couple of thousand dollars more, you can purchase a hot-swappable subsystem that will allow you to replace the failed device without taking down the server.

RAID also provides excellent protection against hard-drive failures, but it isn't a replacement for a backup device. Adaptec has included ProServ CX Lite tape backup software from Sytron Inc. with the AHA-3985 adapter. ProServ uses NLMs on the server to conduct the backup operations, however, a Windows front-end can control the backup process.

ProServ CX Lite doesn't have the features found in packages such as Arcada Backup Exec, but it does offer an easy-to-use backup solution for a small LAN environment. You can use it to schedule backup jobs and make partial backups of modified files.

Like most PCI-bus devices, getting the device up and running is easy because hardware installation is a snap. If you're comfortable modifying your NetWare server configuration, installing the AHA-3985 in your existing file server will be no trouble at all. Once the driver for the AHA-3985 is loaded, simply load the NLM-based RAID management program to create and manage the array.

From the management program, we created a RAID-5 array and selected the drives to be included in the array. The utility also allows you to format the array and check for bad sectors. Once the array is complete, NetWare's installation utility will detect it as a single partition. Creating and mounting the array as a NetWare volume is all that remains to be done.

All essential RAID tasks are built into the AHA-3985 RAID administration utility, including RAID status, media verification, reconstruction, formatting, and changing RAID configuration. We found the status information lacking in detail.

The included SNMP-based CI/O software gives a much better graphical view of controller statistics. When a failure does occur, the server sounds an alarm and displays the hardware failure on the console. The CI/O software also displays an alarm in the administrator's workstation via OpenView SNMP environment. With third-party SNMP products, OpenView can alert you to the problem via pager or e-mail. Once the failed hard drive has been replaced, reconstructing the data can be done only through the server-based utility.

Adaptec indicated that the next generation of adapters and CI/O software will no longer require SNMP, which will allow administrators to schedule a reconstruction of data from an administrative workstation. Using a server console, we were able to schedule a reconstruction at a later time and select a priority level.

Priority level limits the number of reconstruction functions among user requests. When user requests are low, however, the adapter is smart enough to increase the number of reconstruction functions so that the recovery process is speeded up. The manual doesn't provide any guidelines for choosing priority levels, and Adaptec hasn't released any information on the effect of priority level on CPU utilization.

We tested the Adaptec AHA-3985 in our 133-MHz Pentium-based server running Novell's NetWare 3.12 Network Operating System. Our four-disk SCSI array was housed in an external hot-swappable subsystem, the DataSilo. A single client attached to the server acts both as the client and as the management workstation.

AHA-3985. List price: $795; AHA-3985W, $849. Adaptec Inc., Milpitas, CA; 408-945-8600; fax, 408-262-2533; http:\\www.adaptec.com.

Copyright (c) 1996 Ziff-Davis Publishing Company