2950 RAID controllers lack SCSI-passthrough setting

James Ralston qralston+ml.dell-poweredge at andrew.cmu.edu
Mon Feb 19 16:05:09 CST 2007

On 2007-02-08 at 16:25-06 Patrick_Boyd at Dell.com wrote:

> > With PowerEdge 2650 and 2850 servers, the hardware RAID (PERC)
> > controller could be configured to SCSI "passthrough" mode in the
> > BIOS.  In passthrough mode, the system acted like no PERC card was
> > installed; the OS saw the individual disks.
> > 
> > Unfortunately, the PERC controllers in PowerEdge 2950 servers do
> > not seem to offer this functionality: if you disable the PERC
> > controller, you cannot see the disks.
> Please discuss this with your sales and support reps.  If there is
> enough demand for it then future PERC cards may be changed.

Thanks; we told our sales rep that we wanted this feature.

But on a related note...

Is it even possible to order a 2950 with SAS drives and no PERC?

When we asked our sales rep what part we needed to order to make our
2950s a "non-hardware-RAID" system, he asserted that the [non-RAID]
disk controller in the 2950 is SATA only.  Meaning, if you order a
2950 without a PERC, you can only order SATA drives, not SAS drives.
This also why you can't "see" the SAS drives if you disable the PERC:
the SATA controller doesn't know how to talk to the SAS drives.

After we got off the phone, I went and tested using the 2950 order
page.  I could spec a 2950 system without a PERC card and with SAS
drives, and I didn't get any pop-up "Compatibility Instructions".

Is our sales rep wrong?  Will a 2950 work with SAS drives and no PERC
controller?  Is anyone out there using this configuration?

And if it works, what parts do we need to order to make it work?


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