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(Old, Obsolete version of) RAID and Data Storage Protection Solutions for Linux

When a system administrator is first asked to provide a reliable, redundant means of protecting critical data on a server, RAID is usually the first term that comes to mind. In fact, RAID is just one part of an overall data availability architecture. RAID, and some of the complimentary storage technologies, are reviewed below.

Obsolete/Historical data

This page was originally created in 1996, and only sporadically updated. Most of the data below is obsolete. Links are probably dead. This section is here only for historical/archival reasons.

Related References

Hardware RAID Controllers

A hardware controller is a PCI or ISA card that mediates between the CPU and the disk drives via the I/O bus. Hardware controllers always need a device driver to be loaded into the kernel, so that the kernel can talk to the card. Note that there are some devices (which I've listed in the "outboard controllers" section below) that only draw power from the PCI/ISA bus, but do not use any of the signal pins, and do not require a (special) device driver. This section lists only those cards that use the PCI/ISA bus for actually moving data.

Vendors supported under Linux: (Current as of 1998; some of the information below may be rancid.)

Highpoint (New Listing!)
Offer several products, such as the RocketRAID 404 controller which allows four IDE ribbon cables (and up to eight IDE drives) to be attached to the controller. Handy for saving up PCI slots, as IDE is significantly cheaper than SCSI. The RocketRAID BIOS is interesting because it allows hardware-RAID arrays to be built across multiple controllers plugged into the same PCI bus. Thus, for example, a 13-drive hardware RAID array can be built by using multiple controllers.

MegaRAID (New Listing!)
MegaRAID offers the MegaRAID i4 controller for IDE drives features four connectors for IDE ribbons (a total of 8 IDE drives per controller). Supports RAID-5, hot swap and hot spare capabilities.

BigStorage
BigStorage offers a broad line of storage products tailored for Linux.

ICP Vortex
ICP Vortex offers full line of disk array controllers. Drivers are a standard part of the 2.0.x and 2.2.x kernels; the boot diskettes for most major Linux distributions will recognize an ICP controller. Initial configuration can be done through on-board ROM BIOS.

ICP Vortex also provides the GDTMonitor management utility. It provides the ability to monitor transfer rates, set hard drive and controller parameters, and hot-swap and reconstruct defect drives. For sites that cannot afford to take down and reboot a server in order to replace failed disks or do other maintenance, this utility is a gotta-have feature. As of January 1999, this is the only such program that I have heard of for a Linux hardware RAID controller, and this feature alone immediately elevates ICP above the competition.

A RAID Primer (PDF) and Manuals; see Chapter K for GDTmon.

Syred
Syred offers a series of RAID controllers. Their sales staff indicated that they use RedHat internally, so the Linux support should be solid.

BusLogic/Mylex
Buslogic/Mylex offers a series of SCSI controllers, including RAID controllers. BusLogic has been well known for their early support of SCSI on Linux. The latest drivers for these cards are being written & maintained by Dandelion Digital.

DPT
Look for the SmartCache [I/III/IV] and SmartRAID [I/III/IV] controllers from Distributed Processing Technology, Inc. Note that one must use the EATA-DMA driver, which is a part of the standard linux kernel distribution. There are two drivers:
IBM ServeRAID
IBM Intel based servers have onboard RAID.

Outboard RAID Vendors

There are many outboard box vendors, and, in theory, they should all work with Linux. In practice, some SCSI boxes support features that SCSI cards don't, and vice-versa, so buyer beware. Note Some outboard controllers are not true stand-alone, external boxes with external power supplies, but are small devices that fit into a standard drive bay, and draw power from the system power supply. Others are shaped as PCI or ISA cards, but use the PCI/ISA slots only to draw power, and do not use the signal pins on the bus. All of these devices need some other disk controller (typically, the stock, non-raid controller that came with your box) to communicate with. The upside to such a scheme: no special device drivers are required. The downside: there are even more cards, cables and connectors that can fail.

StorComp
Storage Computer is an early pioneer in RAID, and has continued to provide sophisticated, advanced systems, focused primarily on the 'SAN' style architecture. For example, their 'Virtual Storage Architecture' allows multiple CPU's to access the disks through SCSI interfaces. See, for example, their Product Sheet. They also have an interesting collection of White Papers.

www.raidweb.com
www.raidweb.com

Arco Computer Products
Arco Computer offers the DupliDisk EIDE-to-EIDE converter for RAID-1 (mirroring). Three versions are supported: one that fits into an ISA slot, one that fits into an IDE slot, and one that fits into a drive bay.

DILOG
DILOG offers the 2XFR SCSI-to-SCSI RAID-0 product. Features:

Dynamic Network Factory
Dynamic Network Factory specializes in larger arrays.

LAND-5
Offer several products. These appear to be stand-alone scsi-attached boxes, and require no special Linux support. See www.land-5.com

Disk Array Management Software

Most controllers can be configured and managed via brute force, by rebooting the machine and descending into on-card BIOS or possibly DOS utilities to reconfigure, exchange and rebuild failed drives. However, for many system operators, rebooting is a luxury that is not available. For these sites and servers, there is a real need for configuration and management software that will not only report on a variety of disk statistics, but also raise alarms where there is trouble, allow failed drives to be disabled, swapped out, and reconstructed, and for all this to be done without taking the array off line, without halting any server functions. Currently (January 1999) I am aware of only one vendor that provides this capability: ICP-Vortex.

ICP Vortex (New Listing)
ICP Vortex provides the GDTMonitor management utility for its controllers. The utility provides the ability to monitor transfer rates, set hard drive and controller parameters, and hot-swap and reconstruct defect drives.

BusLogic
Buslogic offers the Global Array Manager which runs under SCO Unix and UnixWare. Thus, a port to Linux is at least theoretically possible. Contact your sales representative.

StorComp
Storage Computer offers an SNMP MIB for storage management. MIB's being being what they are, any SNMP tool on Linux should be able to use this to query and manage the system. However, MIB's being what they are, this is a rather low-level, (very-) hard to use solution. See also a white paper on storage management.

DPT
DPT provides management software with their cards. The distribution includes SCO binaries. Thus, a port to Linux is at least theoretically possible. Contact your sales representative.

History

Last updated August 2003 by Linas Vepstas (linas@linas.org)

Copyright (c) 1996-1999, 2001-2003 Linas Vepstas.
Copyright (c) 2003 Douglas Gilbert <dgilbert@interlog.com>

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1; with no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the license is included at the URL http://www.linas.org/fdl.html, the web page titled "GNU Free Documentation License".

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