I'm currently using Mandrake 9.1 (although I plan to go to 9.2 soon...), and I'm curious if anyone knows if I can create a software RAID array between four hard drives. Two of the drives (36GB) are identical and on SATA, the other two are not identical (one 45, the other 160GB) on different IDE cables. I believe it is RAID 0 what I want...for striping instead of mirroring. I can create equaly sized partitions on each drive if necesary, but only two of the drives are of the same speed.

I've played a bit with hardware raid in windows with my onboard controller, and I believe that you need to have each of the drives (or at least partitions) to be of the same speed and size for the array to be effective. Will that cause me problems with my plan using software raid in linux?

How do you guys think this will work performance wise, and what complications I might run into. Unfortunately, won't be able to test it for at least another week until I can find the time.

Thanks.

I'm no expert but I wouldn't build a 4-disk raid in your configuration. I would go with the 2 SATA disks only. You won't gain a lot of performance if you add slower disks to the mix, and I think you'll lose the rest of the big disk.

What kind of controllers are those disks on ?

My motherboard is an Asus A7N8X Deluxe. So aside from the onboard SATA, it uses the Nvidia MCP-T southbridge to control the regular ATA drives. The onboard SATA RAID controller has its own chip on the motherboard separate from the southbridge so the only real limitation I can think of is the speed of the southbridge and its communication to the northbridge.

I understand what you mean by adding the slower drives to the array would slow down the faster hard drives. But I still wander if I wouldn't see an even larger performance gain from the increase in the spread of the data across the drives. I mean, only a fourth of all the data is being written on each drive instead of a half. So even if the faster drives are being slowed down by the slower in the array, the overall output (in theory) would still be much greater.

Also, I'm worried that the cpu overhead for running an array across 4 drives might be too much of a burden. Perhaps it is something I will have to find out on my own.

Please correct me if I'm wrong...I obviously wouldn't be asking around here if I knew anything.