Like the title says, I'm wondering what people recommend in terms of RAID cards under Linux. I'm looking for a PCI-express, SATA card that there's (full?) driver driver support for. Anyone have experiences to share, good or bad, in this area?

It would probably help people if you were a bit more specific. IOW, what are you trying to accomplish? Is it an ego massage or tech toy? Do you have a machine that you don't want to go down if reasonably possible? IOW, is fakeraid RAID0/1 all you're after, or are you looking for a dedicated RAID controller capable of doing RAID5 (etc) without getting the CPU involved?

If all you want is to make a RAID1 to protect your data, then consider using mdadm on whatever controllers you can get cheaply.

I was thinking about hardware RAID5. Sorry about the vagueness in my last post.

According to the README file for DBAN, 3ware is the only SATA RAID controller that isn't software raid. Many cards use the CPU to calculate the parity. The Promise cards are the worst in this regard according to a review site I read.

I have a personal mission against the low-end raid cards; I went through a phase, a few years ago, of thinking that RAID was a neat trick and nothing I tried then really worked (worked in the wider senses of not corrupting & losing your data a bit further on down the road) and so my point of view on them is a little jaundiced.

So my position has changed to the one that the established suppliers (Adaptec, and has been mentioned, 3ware) do this job properly, particularly with SCSI drives and/or Enterprise-class drives that are intended for this kind of duty. Anything else is a bit of a gamble, and you may or may not be happy with that. On the other hand, when you see the cost per gig of the SCSI route, you might not be happy with that, either.

A lot still depends on the purpose of the RAID, which we haven't yet been told. If it's for a home machine, RAID5 is probably serious overkill. If it's for a critical server, then you'll have to throw money at it.

I ran a Promise RAID0 on my home computer for a year on Debian Etch using dmraid. It worked fine but the cables were finicky as hell. For home stuff, the SATA drives and cabling seem very reliable. If you add a quad processor, you should have all the power you need for running a software (mdadm) RAID5 with any inexpensive controller set and still be able to do pretty much anything you want for computing.

3Ware is very well supported in Linux for hardware RAID controllers. LSI is another well supported manufacturer of hardware based cards. LSI Chips are used in a lot of the DELL RAID controllers. The statement, "You get what you pay for" holds true with RAID controllers.

If you truly want a Hardware Based controller that gives you all the bonuses of hardware RAID (take the load off the CPU, allow hot swap of drives, auto rebuild on the fly, array expansion on the fly, etc..) you will pay a premium for such a card.

If the card you purchase is inexpensive then it's going to be fakeraid, which will give you none of the bonuses of hardware RAID and will probably perform worse than just plain old software RAID you wold setup using mdadm and any standard drives & controllers.



3Ware PCI-2,1 4 port SATA hardware RAID controller I believe this can be used in a standard PCI slot, but you will incur a performance penalty for losing the 64 bit access to the PCI bus. Verify with manufacturer rather than taking my word for it.

3Ware PCI-Express 4 port SATA hardware RAID controller

LSI 4 port SATA hardware RAID controller

Only if the underlying hardware is inferior to the other controllers available to you. Fakeraid on Linux uses dmraid, which, in turn, uses the underlying kernel raid modules. Once the kernel boots, all vestiges of the fakeraid's ROM software are gone and it's just another controller, as far as Linux is concerned. However, I haven't looked at the state of dmraid in almost a year, so I don't know where they stand on drive failure recovery procedures, etc. So, hmm, you may be right from that respect. I guess it would depend on the fakeraid's recovery procedures.

Note that I'm not saying that hardware raid isn't better - it is - lots. But, the cheap SATA controllers with fakeraid have gotten pretty good as far as the underlying controller is concerned.

Hey I put the qualifier of 'probably' in there

One other thing I am unsure of is how you would go about installing Linux onto a FakeRAID array.. probably similar to installing on a software RAID array, but neither is as easy as installing on a hardware array.

I'm lazy, I like easy..

Yeah, it was pretty complicated when I did it for Etch. But, I believe that dmraid has made it into the major distros, so it shouldn't be a big issue, now. It's only intimidating because of the use of /dev/mapper and the strange looking device names (e.g. /dev/mapper/gobbledy!@#$gook1). I should try out my old Promise controller just to check if Lenny recognises it during an install. The Ubuntu site is *the* place to go for dmraid help, though.