question about PCI/PCI-64/PCI-X bus sharing

question about PCI/PCI-64/PCI-X bus sharing

Post by Ben Hanso » Wed, 07 Dec 2005 22:47:08


I am getting a new motherboard that has an integrated PCI-X Ultra320
controller built in (Adaptec 7902). Unfortunately the version of the Adaptec
controller used in this mobo is not the version that natively supports RAID,
so I am looking into a zero-channel RAID card to provide that feature.

The motherboard doesn't have PCI-X slots but it does have two PCI 64-bit x
66 MHz slots. Companies like Adaptec that sell zero-channel RAID solutions
say that this won't be a bottleneck to the SCSI and RAID performance, but
how can that be? If the controller itself is PCI-X, then when it accesses
the zero-channel device for RAID operations, won't that slower 64 x 66 bus
slow down the whole process?

For that matter is this setup any better (or different performance-wise)
than just bypassing the onboard SCSI controller altogether and getting a 64
x 66 Ultra320 controller that has integrated RAID and just using that
instead?

My last question is, the mobo also has 2 normal PCI slots (32 x 33). Are
these a separate bus from the 64 x 66 slots? I want to install a cheap PCI
vid card in the normal PCI slot but if the bus is shared that will destroy
my 64 x 66 device performance, right?

-Ben
 
 
 

question about PCI/PCI-64/PCI-X bus sharing

Post by Pete » Wed, 07 Dec 2005 23:29:19

> I am getting a new motherboard that has an integrated PCI-X Ultra320
Adaptec
RAID,
64

What is your motherboard make/model?

 
 
 

question about PCI/PCI-64/PCI-X bus sharing

Post by Ben Hanso » Thu, 08 Dec 2005 01:19:11

Supermicro P4SC8

I needed this one cause my proc at this time is a P4 Prescott (478).
 
 
 

question about PCI/PCI-64/PCI-X bus sharing

Post by Pete » Thu, 08 Dec 2005 02:02:08

> Supermicro P4SC8


64-bit

Those two are PCI-X slots (64-bit, 66MHz, 3.3V)

but
accesses

There is no mismatch, so there is no slowdown. This bus is up to 533MB/s.

performance-wise)
a

There is no point in doing that (from bus perspective) but some other
controllers might be simply better.
So you have lots of fast SCSI disks?

Are

Yes, they are on a separate bus.


It is not shared.
 
 
 

question about PCI/PCI-64/PCI-X bus sharing

Post by Folkert Ri » Thu, 08 Dec 2005 03:44:03

The real question is, is your MoBo Zero Channel Raid compatible.



"The chip features a 66 MHz, 64-bit PCI interface *and* a 133 MHz, 64-bit PCI-X interface".


Sounds unlikely. More likely it isn't implemented in the BIOS.


AFAIK, that needs a specially designed MoBo. Is your's?


And likely does not have PCI-X either.


The same bus that the Adaptec chip is likely connected to.



It's not. Only if connected to a PCI-X bus.


64x66 = 533 MB/s minus overhead
2*U320 = 640 MB/s minus overhead
SCSI's overhead is bigger than PCI's, that narrows the gap.
And you'll only go into that territory if your devices actually need all that bandwidth.



Read the specs?
If they were to be on the same bus they likely be 32x66, not 32x33.


In your 64 x 66 bus slots, yes.
 
 
 

question about PCI/PCI-64/PCI-X bus sharing

Post by Ben Hanso » Thu, 08 Dec 2005 04:01:26

Thanks Peter. In my application I have 4 Ultra320 15K drives in a RAID 0
array. So I guess what I was thinking was that although I know the
integrated controller and the zero-channel card/PCI slot are both PCI-X,
that the former is at 133 MHz where the latter is only at 66 MHz. And so it
seemed to me that between the card and the integrated controller was a
bottleneck. Am I just not understanding how the integrated SCSI controller
and the zero-channel RAID card interact with one another?

-Ben
 
 
 

question about PCI/PCI-64/PCI-X bus sharing

Post by Pete » Thu, 08 Dec 2005 04:41:02

> Thanks Peter. In my application I have 4 Ultra320 15K drives in a RAID 0
it

ZCR card, what card? Supermicro recommends Adaptec 2010S. Is that what you
have? That card is also 64-bit/66MHz PCI. Your MB has 64-bit/66MHz PCI-X
slots.MB chipset (6300ESB) has also 64-bit/66MHz connection to PCI-X.
Bottleneck? Of what sort? What kind of application is yours?