[K12OSN] Woe is me: Onboard SCSI/RAID Controller

[Brian Chase]

I notice there's alot of discussion here about the different on-board 
RAID controllers.  Most, if not all, SCSI controllers, on-board or 
otherwise, should be found by any Linux distributions.  The problem you 
have is the RAID chipset manufacturers that are in bed with Microsoft 
and take hardware design shortcuts on the actual hardware RAID and 
borrow resources from the Windows OS.  Promise Technologies is just one 
notorious for this with their onboard IDE RAID implementations.

There's countless ways to approach this, as indicated by the variety of 
responses on this thread, but I'd give the idea of disabling the 
motherboard RAID a try and consider 3ware controller cards for real 
Hardware RAID in Linux if you're doing anything with IDE drives.  My 
understanding is that the newest K12LTSP's come with SATA support does 
actually recognize an on-board Promise SATA chipset, but it would 
require specific checking on the chipset before money is spent.




Robert Arkiletian wrote:

>Hi Debbie,
>I have good news. I am using this SCSI controller chip AIC7902W with super
>stability/performance in my school. I researched the chip before I bought it. It
>has very affordable scsi performance.
>
>I got an intel server board with the chip. The docs say it supports HOST raid.
>However, Linux does NOT support Host Raid. Host raid is actually software raid
>for Windows (ITS NOT HARDWARE RAID). There are drivers for Windows to make it
>work but not for Linux. However, the linux kernel will support software raid
>using LVM, which is just as fast as some hardware raid setups. (Although I have
>not tried it, I know it's done when you setup your partitions) The beautiful
>aspect of the AIC7902W is that is has TWO scsi channels. So you can have the
>full throughput of each channel and raid them through the kernel. All I did was
>use one scsi drive for / and another for /home. I have not tried raid. I'm using
>k12ltsp 3.1.2 (redhat 9) and not 4.1.1 (FC2). 32 clients == no problem.
>
>A couple of notes. You MUST disable HostRaid in the bios for the controller to
>work with Linux. Also, I down graded each scsi channel to 160 mb/s instead of
>the 320 mb/s (default). The system was not fully stable at 320mb/s because of
>scsi driver issues. Don't worry though a new 10k rpm scsi drive only needs
>around 60 mb/s bandwidth. So you should be okay for about 3 drives/channel at
>full throttle for all of them (highly unlikely). I don't think you will ever
>need more than 6 scsi drives for k12ltsp. The driver for the kernel is written
>by Justin Gibbs. He had some issues/disagreements with James Bottomley (kernel
>maintainer) and Linus Torvalds. So he pulled the drivers before version 2.0.x
>from his site. The 2.6 series kernel has stable adaptec scsi aic79xx driver
>1.3.x in it. But if you go with k12ltsp 4.0.1 (FC1 & kernel 2.4.22) or earlier
>you will have to use a driver update disk (DUD) from here (versin > 2.0)
>
>http://people.freebsd.org/~gibbs/linux/
>
>these are stable too but the kernel maintainers are wary of them for technical
>reasons beyond my comprehension.
>
>This DUD disk has to be made with "dd" and must be used during installation of
>the OS in Expert mode.
>If you go with k12ltsp 4.1.1 (FC2) , no worries, it has stable scsi adaptec
>aic79xx driver 1.3.x built in since it comes with kernel 2.6.5
>If I was you, I would go with k12ltsp 4.1.1 (FC2) from the beginning. It will be
>the easiest for you. I did not have this option when I started. Just don't
>forget to disable HostRaid in the SCSI bios and lower the throughput to 160mb/s
>for each channel and you should be good to go. Also make sure your scsi cables
>are high quality and terminated properly.
>
>Hope that helps
>Good luck
>
>BTW the drivers on adaptec/intel sites are very old (don't use them)
>
>Robert Arkiletian
>
>
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