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Intel ICHxR raid 0 drivers

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December 7, 2008 1:26:54 PM

I am planning a Raid ) installtion using the on-board intel ICH8R, I'm a little confused by the need for driver software. I'm comin g from a server background using SAS/SCSI hardware raid solutions where the OS just sees whatever virtual volumes I create via the Raid card BIOS, no need for drivers at all.
Everything I have read about using radi 0 on Intel chipsets suggests I need to either hit F6 for floppy / slipstream install the drivers.

So, steps-

1) enter BIOS, setup raid volume
2) start XP install, hit F6, load drivers
3) install XP
4) REBOOT!

OK - this is where I get confused, because now

5) XP loads off the RAID 0 volume.

My question is how? The drivers XP needed to read the RAID 0 volume are now on the RAID 0 volume. How is it that XP can now read the volume without loading the drivers? If XP can do this why is it XP needs the drivers for the installation?

I fully appreciate that I'm just going to have to do a driver install, just curious if anyone explain what is going on here to me.

Stuart
December 7, 2008 6:17:07 PM

Onboard RAID, Fake RAID, Hybrid RAID, Driver RAID, Firmware RAID are all the same thing: usually the chipset offers a RAID mode allowing the use of RAID0, RAID1, RAID10 and sometimes RAID5 while still being able to boot from it.

You said:
Quote:
The drivers XP needed to read the RAID 0 volume are now on the RAID 0 volume. How is it that XP can now read the volume without loading the drivers?

This is exactly the reason why you cannot boot off a software RAID array; since the drivers required to read from the array are on the array itself, there is the chicken and the egg problem. The solution for onboard RAID is to use a simple bootstrap; a minimalistic and often read-only implementation of the supported RAID levels are programmed into the CMOS, this is called firmware which is essentually software in the hardware.

It will attempt to read configuration data in the last sector (512 bytes) of each drive, where it usually stores its data. There it can see you have a 2-disk RAID0 array with both disks accounted for, and can boot from it like you were booting from a hardware RAID controller.

The difference with (true) Hardware RAID is, that after the operating system is loaded, RAID drivers on the kernel-level take over, hide your physical disks and present itself as a SCSI controller which Windows can use. The actual work is done by drivers on your system, just like Software RAID. If you boot Linux or BSD you still see the two drives; nothing the controller does more than act as a normal SATA controller; it only provides a BIOS setup utility and BIOS bootstrap support by flashable firmware. With Hardware RAID, the operating system can never directly communicate with the physical disks, and has no knowledge about it being a RAID volume at all, all it knows its a SCSI controller requiring a driver to send and read from. Using Windows Vista you can also the newer Storport-drivers, a next generation interface to overcome some of the limitations of the SCSI software interface.

By the way, Intel ICHxR is probably the best onboard RAID controller found on desktop motherboards. You can enable write cache (though it is actually a buffercache) for extra performance, at the cost of increased filesystem corruption upon unclean shutdown/crash/powerdown etc. Since you already RAID0, the added risk is mostly irrelevant since you ought to have proper backups anyway. If that is not the case then you should really leave this option disabled.

Without this option, HDTune will not yield proper results. Never trust HDTune to work correct on RAID arrays, it accesses the storage device in a too primitive fashion for it to yield useful results. Try ATTO-256 instead, which acts on the Filesystem-layer.
December 8, 2008 8:14:44 AM

Great answer - thanks a lot!

Stuart
!