RAID in Linux

[AndrewB]

This is very techie, so if you really don't care then feel free to ignore this post.

What's the best solution for RAID on a Linux box?

- Hardware RAID? (If so, what motherboards can do it?)
- RAID 5 available with hardware solution?
- Super ATA for speed?
- VIA motherboards are supposedly terrible for RAID in Linux. What about ABIT?
- How do I avoid fake RAID? (I.E. a software RAID program or BIOS RAID)

[Bloodshedder]

Lots of motherboards have integrated hardware RAID now, but very few offer RAID 5. Most just do 0, 1, and 0+1. I would go with Serial ATA (not "Super" ATA) for my hard drives.

VIA doesn't make motherboards, they make chipsets, but I'm not sure if they make RAID controllers. Motherboards with integrated RAID either will use nVidia's RAID controller in nForce4, or a separate Promise RAID controller. Most motherboards with integrated RAID will come with a separate utility on a disk that you boot from to set up your RAID sets.

Hardware RAID is really OS independent, so neither Windows nor Linux will really care how your RAID setup works. It just sees a plain old hard drive, depending on however you set up your RAID volumes.

[Remilia Scarlet]

There should be a RAID 5 hardware solution. We have a Sun V40z server that supports it, so I do know it exists. Whether it does in consumer motherboards is another question, though. Some Intel boards might support it, come to think of it.

SATA drives will definitely help peformance, but you should also consider higher RPM drives and/or SCSI. A drive's RPM can be a real bottleneck.

What's really fun to do after you have the RAID setup is to use LVM on top of it.

[AndrewB]

I'll have to find out what LVM is; it sounds like there's a joke in there somewhere.

I'll probably just end up doing RAID 0 with three disks or something. I'm using MySQL 5.0, and I would like to keep the tables and the indexes on separate, independent drives. That would probably require at least 4 drives, though.

[Bloodshedder]

Note that RAID 0 involves "zero" fault tolerance, because if one drive fails, all your data goes kaput. If you're using four drives, use RAID 0+1 or 1+0 instead, or RAID 5 if possible (but 5 only requires three drives).

[AndrewB]

You're right; I always remembered the FS or FileSystem rule, where 0 was Fast and 1 was Safe.

I meant, of course, that I might use three disks of RAID 1. Or maybe two; who knows.

[Remilia Scarlet]

LVM is the Logical Volume Manager thing in the kernel.

http://en.wikipedia.org/wiki/Logical_Volume_Manager_(Linux)

Basically, you create volume groups, which are made up of logical volumes, but you can perform online resizing on those at will. I remember doing them on top of both a RAID 1 and RAID 5 array during RHCE training.

[exp(x)]

Since my motherboard only has fake raid, I had to use software raid. Unfortunately, you can't boot off of a software raid 0 array, so what I did was create a tiny raid 1 boot partition and then I filled the rest of the drives with raid 0 and swap. I used the partition thingie that comes with the ubuntu installer. It was pretty easy to set up once I realized that this was what I had to do, but figuring it out was a bitch.