On Sun, Oct 24, 2004 at 08:28:35PM -0500, Ron Johnson wrote:
> On Sun, 2004-10-24 at 12:58 -0400, Lennart Sorensen wrote:
> > On Sun, Oct 24, 2004 at 12:04:48AM +0900, Nils Valentin wrote:
> [snip]
> >
> > A SiS3114 is NOT hardware raid. It is software, just secret proprietary
> > software. If you want hardware raid with open source drivers, you have
> > to get a 3ware card or a scsi raid card. Those are the only choices at
> > the moment. Other hardware ide/sata raid cards exist, but not with open
> > source drivers that I am aware off.
>
> Isn't *all* real h/w RAID "just secret proprietary software" on
> the RAID controller? Whether it be in flash or an EEPROM, real
> h/w RAID controllers have a dedicated (usually specialized) CPU
> for handling the RAID calculations, SCSI commands, RAM cache, etc.
>
> Thats why when you call up IBM, HP or Sun with a disk-related issue,
> they ask you if your SCSI cards & RAID controllers are at the latest
> ROM version.
THe difference in this case being that the SiI3114-based cards
_don't_ have an on-board CPU to offload the RAID processing overhead.
Therefore, the host CPU has to perform the RAID processing, and the
load on the system bus correspondingly greater as well. This is what
is commonly known as "software RAID". The BIOS on the card is
sufficient to be able to read a particular (proprietary) header on the
disks and start the boot process from them. It may also contain a
configuration tool to set up this header.
Hugo.
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