fakeraid/dmraid and PowerEdge SC440

Jeff Garzik jgarzik at redhat.com
Mon Dec 18 20:06:51 CST 2006

On Tue, Dec 19, 2006 at 12:38:51AM +0000, Kevin Davidson wrote:
> Hi
> I'm setting up a brand new SC440 with SUSE (actually openSUSE 10.2  
> x86_64). It has a pair of 250Gb SATA disks, and when ordered the  
> option was ticked that they be cabled up for RAID 1. The config  
> ordered should be using the onboard Intel ICH7 SATA controller to  
> support the mirroring.
> However Linux sees the 2 disks as separate drives. There is nowhere  
> in the BIOS menus to turn RAID1/0 on or off - just to turn each of  
> the SATA drives 0-3 on or off. Running "dmraid -ay" (or any other  
> dmraid command reports that there are no RAID disks available. I'd  
> hoped the installation setup CD would help, but all that did for me  
> was set the clock :-(
> Am I doing something wrong? Using the wrong version of dmraid/ 
> fakeraid (it's 1.0.0.rc13 which seems to be the latest)? Using the  
> wrong ATA driver? Or am I just stuffed?

There is no such thing as "RAID cabling" in SATA.  All of SATA
controller<->drive point-to-point connection.

If it is attached to the ICH7 SATA controller, then you have no RAID
capability in your hardware.  Thus, the ATA driver presents exactly what
the hardware presents.

Just like MD (normal Linux software RAID 0/1/2/5/6/...), dmraid is a
pure software RAID layer.  Normally, as you suspect, this is setup in
BIOS.  If you do not have software RAID setup in BIOS, then dmraid will
obviously not be able to find the RAID setup created by BIOS.

But honestly, why bother?  It's all software, so just use the
production-tested Linux software RAID driver (MD).


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