Re: sata_sil24 stability and performance

[Denys Dmytriyenko <denis@denix.org>]

On Thu, Mar 06, 2008 at 04:08:48PM +0900, Tejun Heo wrote:
> Denys Dmytriyenko wrote:
> >>> Also, few months ago instead of sata_sil24 I had my drives connected to
> >>> sata_mv (Supermicro 8-port) and performance was normal...
> >> Everything seems okay.  I wonder where the difference is.  Does "dd
> >> if=/dev/zero of=file oflags=direct bs=1M" make any difference?  And can
> >> you vacate a raw partition and try it on there?
> > 
> > oflag=direct has no effect - same speed. Tried it on a raw /dev/sda device
> > and still no difference. It maybe slighly better, giving me 18 MB/s.
> > 
> > Can it be something with the way SiI 3124 controller is configured in the
> > system?
> 
> Hmmm... That's strange you did specify the "bs" parameter, right?  It
> should essentially give the same performance as "hdparm -t".  I wonder
> where the difference comes from.

Ok, after countless night-hours trying different configurations and peripheral 
combinations, it seems I can get good write performance (55 MB/s) from SATA 
card sitting in PCI-X slot, but bad write performance (18 MB/s) when it sits 
in PCI slot. And it is far from the PCI bandwidth limit.

I did some research and found out that apparently it is a known issue of 
AMD-760 MPX chipset. PCI-X bus is on the AMD-762 north bridge, while PCI bus 
is on the AMD-768 south bridge, which has a write bandwidth limit of 25 MB/s 
"bug", acknowledged by AMD. See these discussion threads:

http://forums.2cpu.com/showthread.php?s=c8040a4e9c9b6390dd389f1b3cca32de&threadid=31211
http://episteme.arstechnica.com/eve/forums/a/tpc/f/77909774/m/1160910035
http://forums.2cpu.com/showthread.php?s=66da493f719e8e64d15dc974cd567192&threadid=23379

Now, I have 2 options:

1. Keep existing system, but utilize 2 PCI-X slots for SATA controllers. This 
requires using 8-port adapters, like the one I already have Supermicro Marvell 
based. The question is - how stable sata_mv these days? It still says HIGHLY 
EXPERIMENTAL...

2. Replace MoBo+CPU+RAM (at least) and keep using SiI3124 based 4-port SATA 
adapters, as sata_sil24 is supposedly the most stable solution I can get.

I'm leaning towards the second option, but it would cost me more, compared 
to getting the second Marvell based PCI-X SATA card. Can you please advise? 
Thanks in advance.

Regards,
Denys