Performance Advantage with Onboard SCSI Controller?

I'm in the process of upgrading my system and I'm leaning towards
either the GA-8KNXP or GA-8KNXP Ultra mainboard. In my current
system, I have a 15K U320 SCSI HDD with an Adaptec 29320-R contoller
card. This serves as my system drive. My remaining drives are
Ultra-133 IDE running off of a (PCI) Promise controller card.

I've read many of the previous threads regarding the pros and cons of
onboard SCSI, and the consensus seems to be that it's probably worth
it for those who who would otherwise need to buy a separate controller
card, mostly because of the cost savings. This of course doesn't apply
to me because I already have the card. However, I'm wondering if there
are any performance advantages offered by an onboard controller vs. a
controller card running in a PCI slot. For example, my understanding
is that despite the internal capabilities of my Adaptec card and HDD,
performance is still limited by the PCI (32-bit) maximum bandwidth of
133Mb/s. Furthernmore, I've been told that all of the PCI slots must
share that same bandwidth. I would assume (and we know what that means
) that any onboard controller (whether it's SATA, IDE or SCSI) would
benefit from having it's own dedicated channel and would therefore not
have to share those resources with any other devices. Is this true?
I realize that with only one SCSI HDD, I'm probably not going to see
any difference. On the other hand, if I eventually add additional SCSI
device, then it may become more of a factor.

Is there any validity to this argument or would I still be better off
choosing the non-ultra version of the mainboard, using my existing
Adaptec card and saving the few extra $$$$.

Thanks in advance for your input.

- Tom

Tom,

I believe that on board SCSI is subjected to the same bottlenecks as a PCI
SCSI. I am sure the world would have been jumping up and down if the onboard
had the advantage. For SCSI III that would be substantial if true.

Since you already have the controller, I would suggest saving bucks and
getting the non ultra board, bearing in mind that the Ultra download site
mentions 'RAID' capabilities for the onboard controller. I suspect this RAID
capability is implemented in the Driver, not the controller, so it is more
akin to a soft RAID and will not give the best performance boost. I hope I
am wrong here.... it would be excellent if it implemented h/w RAID.

Once you have SCSI, stick with it. The closest in performance to Ultra320
would be Raptors. Tom's H/W guide did some benchmarks on Raptors and they
came out well... The price difference between a 36 GB raptor and a 36 GB
SCSI disc is negligible (last I looked), but for most people Raptor has the
price benefit of not needing a SCSI controller.

As you no doubt know, the SCSI drives are substantially more reliable, have
5 year manufacturers warrantees (never buy one off a supplier that will not
honour 5 years), and have much better Seek times. Apart from the Raptor,
SCSI 320 discs are faster in all respects. Compared to IDE, SCSI has much
better support for multitasking O/S (IE supports overlapped IO's, command
queue's, scatter gather etc.), so if you run server class s/w on a server
class o/s (NT or later) you will get much better & smooother performance in
a multi-task, multi-programming system. (IDE RAID supports some of this).

So, this should not be the final word. To saturate your SCSI 320, you need 4
drives, with only 1 drive you are unlikely to see benefit of say PCI-X
interfaces due to the overall data throuput of 1 drive. Save bucks, get
another drive, performance will be even better

- Tim




"Tom T." <tom_townsend.TakeThisOut@comcast.net> wrote in message
news:b5ca996.0310180551.70800bc4@posting.google.com...
 > I'm in the process of upgrading my system and I'm leaning towards
 > either the GA-8KNXP or GA-8KNXP Ultra mainboard. In my current
 > system, I have a 15K U320 SCSI HDD with an Adaptec 29320-R contoller
 > card. This serves as my system drive. My remaining drives are
 > Ultra-133 IDE running off of a (PCI) Promise controller card.
 >
 > I've read many of the previous threads regarding the pros and cons of
 > onboard SCSI, and the consensus seems to be that it's probably worth
 > it for those who who would otherwise need to buy a separate controller
 > card, mostly because of the cost savings. This of course doesn't apply
 > to me because I already have the card. However, I'm wondering if there
 > are any performance advantages offered by an onboard controller vs. a
 > controller card running in a PCI slot. For example, my understanding
 > is that despite the internal capabilities of my Adaptec card and HDD,
 > performance is still limited by the PCI (32-bit) maximum bandwidth of
 > 133Mb/s. Furthernmore, I've been told that all of the PCI slots must
 > share that same bandwidth. I would assume (and we know what that means
 > ) that any onboard controller (whether it's SATA, IDE or SCSI) would
 > benefit from having it's own dedicated channel and would therefore not
 > have to share those resources with any other devices. Is this true?
 > I realize that with only one SCSI HDD, I'm probably not going to see
 > any difference. On the other hand, if I eventually add additional SCSI
 > device, then it may become more of a factor.
 >
 > Is there any validity to this argument or would I still be better off
 > choosing the non-ultra version of the mainboard, using my existing
 > Adaptec card and saving the few extra $$$$.
 >
 > Thanks in advance for your input.
 >
 > - Tom<!-- ~MESSAGE_AFTER~ -->