frankieh wrote:
Also of interest to me is the SATA raid as I'd like to setup future servers to use striping/mirroring, but only if its software transparent. (So I mean is the RAID provided by these boards the same as pluggin in a SCSI raid controller such that linux will then see the drives as one, without using software raid.? ) the board specs on SATA:
Serial ATA Interface
- Support 2 serial ATA plus 1 ATA133
- RAID O or 1 is supported
- RAID function works w/ATA133+SATA H/D or 2 SATA H/D
The board I am looking at, is the top of the line MSI board.
http://www.msicomputer.com/product/p_spec.asp?model=K7N2_Delta-ILSR&class=mb
The onboard RAID chips are software RAID, same as the cheap PCI IDE RAID controllers you can buy. I.e. the motherboard CPU is responsible for addressing each of the drive controllers in turn and telling them to write to the drive. As such, there is a performance hit.
You can run them in a transparent mode. During boot you are presented with the usual BIOS startup together with "Press DEL (or whatever) to enter setup". Ignore that and another screen follows which is the same sort of thing but for the RAID controller. If you enter the RAID controller setup screen there, then you can format drives and setup RAID sets. This then presents your operating system with a single logical drive and lets the RAID BIOS handle all the fiddling about.
I suspect I'm probably telling you a lot of stuff you already know, but... when your OS (be it Windows, Linux or anything else) calls the BIOS disk write routine for your logical drive, it sends the appropriate info to each of the physical drives setup in your configuration. As far as the OS is concerned you've only got one drive but as far as the processor is concerned you've got two (or more) - it's still doing the same work in the same way as if you had configured the RAID array in your operating system, just on the other side of the OS/BIOS dividing line.
So the answer to your question is both YES (you can make it software transparent) and NO (it's not the same as a SCSI hardware RAID controller).
Additionally, it's generally accepted (i.e. people tell me but I haven't done any tests myself) that the software RAID in the Linux kernel is faster than the transparent software RAID you get through an onboard RAID controller. If you ARE going to go this route then my recommendation would be to grab a copy of mdadm and do it in Linux... but I know that isn't what you want to do :-)
Another advantage of doing it in Linux is that you can use RAID-5 which the motherboard RAID chipsets and the cheaper hardware RAID cards don't support.
Jon
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