Re: southbridge/sata controller performance?

[Roger Heflin <rogerheflin@gmail.com>]

Matt Garman wrote:

> 
> Are you talking about using additional SATA controllers (i.e. via
> add-on cards)?  Or simply talking about the interconnect between the
> southbridge and the northbridge?
> 

Don't count on it, it depends on the specific setup of the MB.

> I think you're talking about the former, i.e. the SATA controller
> integrated in the southbridge generally ought to be fine, but if you
> start adding additional controllers that hang off the south bridge,
> their could be competition for bandwidth to the northbridge...
> right?  (And wouldn't the nvidia chips have an edge here, since they
> have everything combined into one chip?)

Again, it depends on how much bandwidth was allocated internally in 
the chip just because it is one chip does not mean that anyone 
actually allocated enough resources to the given part of the chip, or 
even has enough feed to the chip to support them all.   The Seagate 
1.5's will stream quite a bit higher numbers than previous disks, so 
if one had several of them they could overload the allocated 
bandwidth.   Things build-into a given MB aren't always connected at 
full speed often some of them are actually pci bus parts and suffer 
from slow access, I would expect there to be similar tradeoffs even in 
single chip cases.

> 
> Makes intuitive sense anyway; but in my case I'm really just curious
> about the SATA controller integrated into the southbridge; not
> concerned with additional SATA controllers.
> 

The build-in intel ich series controllers vary from version to version 
on exactly how fast that they are in this test, the newer ones are 
faster than the older ones.

> 
> Is the "parallel dd test" valid if I do a raw read off the device,
> e.g. "dd if=/dev/sda of=/dev/null"?  All my drives are already in an
> md array, so I can't access them individually at the filesystem
> level.
> 
> Thanks for the feedback and info!
> 
> Matt
> 
> 
Yes, that is valid, so long as the md device is fairly quiet at the 
time of the test.  Since you already have a machine, please post the 
mb type, and number/type of sata ports and the 1-disk, 2-disk, 
3-disk,... numbers that you get.

I am looking at getting a new AMD solution in the next month or so and 
would like also know which scales reasonably.