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Re: "rock solid" motherboard

On Saturday 12 March 2005 02:56, Superuserman wrote:
> Paul wrote:
> >> The Linux kernel does not now support any of the
> >> motherboard chips capable of native RAID mode in the
> >> BIOS.
> >
> > Not true. Read
> > http://linux.yyz.us/sata/faq-sata-raid.html.
> Perhaps you missed the subject matter. The question is why
> the ABIT AV8 RAID mode in the BIOS does not work with Linux.
> The drivers in the kernel don't control whether the BIOS has
> RAID mode enabled or not; that is in the BIOS. Nor was the
> original question about raid programs instead of chips.
> The ABIT AV8 and my ASUS A8V both have the VIA8237 chip. The
> problem with the VIA8237 is the same as all the rest: the
> chips are not supported by the kernel in RAID mode. There
> are probably people someplace hacking around the kernel
> drivers and maybe they will get things working someday.
> All disk controllers built into AMD64 motherboards, if they
> have RAID capability, are only supported if RAID mode for
> the chips is not enabled. Do NOT enable the RAID mode for
> the chips in the BIOS or they won't work using the drivers
> in the kernel because the drivers were not written to use
> the controllers properly if RAID mode was enabled.

And you're missing the point of my reply. The VIA chips have absolutely no 
hardware raid functionality. Anyone who tells you otherwise is either lying 
or badly misinformed.

Setting the "raid option" in the bois does absolutely nothing to the hardware, 
it just enables the bios emulation so you can boot off your raid set. As soon 
as you boot an operating system (windows or linux) that then talks to the 
hardware directly, so the bios setting has no effect.

All the raid functionality for these chips is implemented in software by the 
bios and/or the OS drivers. Install/setup the prober linux drivers (dmraid et 
al) and you will be able to access your "bios raid" partitions. This is no 
different to windows: Your hardware won't work unless you install the correct 

> > Most (maybe all?) of the proprietary raid formats are
> > supported by the dmraid driver.
> Maybe the DiskMapper code is the exception except the chips
> are no good anyway.

Huh? Exception to what?

> > Generally speaking RAID0 doubles throughput for large
> > writes as data is striped across both volumes, and has
> > seek times the same as a single drive.
> Not for chips on any AMD64 motherboard. This is not about
> theory, this is about certain chips and how they work and
> they don't work good enough to use their RAID capability.
> Read this and weep:
> http://techreport.com/reviews/2004q2/chipset-raid/index.x?pg=28

The graphs that article show exactly what I said. It also shows that some of 
the bios/windows drivers really suck, but that's hardly surprising. It's also 
irelevant if you're running linux.

> Paul, what motherboard do you have? How do your disk
> controller chips perform?

Tyan Thunder K8W (2885) with Sil3114 (equally cheap onboard raid chipset). It 
all works fine (two-disk md raid0). Enabling the raid function in the bios 
does precisely nothing once you boot an operating system (DOS doesn't count 
as an operating system here, it's just an overgrown bootloader).


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