split backplane on PowerEdge 2650: win or no?

Steve_Boley@Dell.com Steve_Boley at Dell.com
Fri May 21 16:59:01 CDT 2004


Can purchase daughtercard and 2nd scsi cable from spare parts
and run split bplane with sware raid.
J0661 is the cable
3D735 is the daughtercard
With the daughter card inserted it will automatically split when
you attach the 2nd cable to it.  This will offload the commands
to 2 of the drives to a separate controller so it will help but
I'm not sure how much and would really show benefit under load.
The 7899s are on 64bit 66mhz bus of it's own so the prev statement
of 33 was incorrect so it definitely would be to your advantage to
split the controllers.
Steve 

-----Original Message-----
From: linux-poweredge-admin at dell.com
[mailto:linux-poweredge-admin at dell.com] On Behalf Of Mick, Jason
Sent: Friday, May 21, 2004 4:46 PM
To: qralston+ml.dell-poweredge at andrew.cmu.edu; linux-poweredge at dell.com
Subject: RE: split backplane on PowerEdge 2650: win or no?

You can either use the internal channels of the ROMB or an addin PCI
RAID card to attach to a split backplane.  The ROMB will be cableless
design and the addin will attach to the two connectors on the backplane
that say SCSIA and SCSI B.  You will have to use a daughter card to
terminate the backplane in split-bus mode.  Please beware that if you
attach an addin RAID card to both sides of the backplane without a
daughtercard it will split however will not have correct termination and
you will probably start to fail drives.  

If you are using an add in RAID card (perc 4/dc) you will have to use
both channels to attach to the internal backplane.  You cannot configure
a split backplane to be half on the internal RAID (ROMB) and half on a
PCI card(PERC 4/DC).


Hope that helps...

Jason Mick
 

-----Original Message-----
From: linux-poweredge-admin at dell.com
[mailto:linux-poweredge-admin at dell.com] On Behalf Of James Ralston
Sent: Friday, May 21, 2004 4:02 PM
To: linux-poweredge at dell.com
Subject: Re: split backplane on PowerEdge 2650: win or no?

On 2004-05-21 at 21:40:16+01 Colin Whittaker <colin.whittaker at heanet.ie>
wrote:
> My understanding from having tried to order such a configuration is 
> that the split backplane is only available if you order the onboard 
> raid card.

Hmmm.

>From this:

http://support.jp.dell.com/docs/systems/pe2650/en/sm/remove.htm#1047004

...it certainly seems as if you don't need the onboard RAID.

On Dell's website, I can spec out a PowerEdge2650 system with the split
backplane and no add-in controllers.

Although I do see this disclaimer under the "Hard Drive Configuration"
section:

   "Split Backplanes requires Primary Controller with a minimum of 2
    internal channels"

This doesn't seem very clear.  :(

James

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