Re:Last time I checked (Score 5, Insightful)

Been using Linux SW raid in the 2.4 kernel series for a year+ now and it has worked like a champ, with both IDE and SCSI devices. All disk servers were SMP (overkill but management wanted it that way). Dunno what you screwed up.

If your criteria for an adequate disk server include either (a) high performance or (b) long-term maintainability, then you should choose SW raid.

Most HW raid systems, especially cheapo PCI cards, but even expensive Fibre Channel-SCSI3 rackmount monsters, offer either extremely primitive performance metrics or none at all. With SW raid, you normally get the full performance-monitoring and tuning capabilities of the host OS. Big win. You will also get better performance from a SW raid, given the same drive layout, and as long as you do not use the box for anything else at the same time. It should be obvious but some people don't believe this.

The other big win is more important when you spend more money than $3000 (a pittance in this market): there's no hardware manufacturer to get bought, go out of business, or change product lines. No multi-thousand-dollar support contract or custom software to configure the RAID or any of that other crap. Trust me, when your dedicated RAID box's motherboard flakes on you and you discover the manufacturer has gone out of business, you'll be cursing yourself for choosing HW raid every time you search Ebay for a replacement part.

Not to mention that commodity, general-purpose HW is always cheaper to replace, and its performance/price ratio grows much faster than special purpose HW. The HW raid system with the 200MHz i760 and 64MB RAM might have looked great in 2000 but now you're stuck with the proprietary on-disk format of an out-of-business vendor with no way out except to build a new system of the same capacity and copy everything over. (In the case of large data warehouses, "full backups" don't usually happen.)

HW raid was compelling in the past. Now, with commodity hardware so cheap, and open, stable SW raid systems floating around, you'd be a fool not to prefer them in many situations. If you want a fire-and-forget dedicated box, go for it. But be ready for the "forget" part in a year or two.