Adaptec 1405 on FreeBSD

[Alexander Motin]

Dieter wrote:
> In message <4B0176E7.7080204 at FreeBSD.org>, Alexander Motin writes:
>>>>> - SiI3124-based - fast and functional. It is actually PCI-X one, but
>>>>> there are many boards with built-in PCIe bridges.
>>> Do any of these fit in a x1 slot?
>> I was surprised, but yes.
> 
> My google-fu fails me.  Any make/model, URLs, or keywords?

Syba PCI Express SATA II 4 x Ports RAID Controller Card SY-PEX40008

http://www.amazon.com/Syba-Express-Ports-Controller-SY-PEX40008/dp/B002R0DZWQ/ref=sr_1_22?ie=UTF8&s=electronics&qid=1258452902&sr=1-22

>> And as expected, bus limits it performance
>> badly. But it is still works much faster then 3132 at the same bus.
> 
> Hmmm, I must not have tested both disks at once before on the 3132:
> 
> One at a time:
> 
>    dd if=/dev/ad18 bs=1m count=1000 of=/dev/null
>    1048576000 bytes transferred in 8.807009 secs (119061534 bytes/sec)
> 
>    dd if=/dev/ad20 bs=1m count=1000 of=/dev/null
>    1048576000 bytes transferred in 8.800526 secs (119149243 bytes/sec)
> 
> Two at once:
> 
>    dd if=/dev/ad18 bs=1m count=1000 of=/dev/null & dd if=/dev/ad20 bs=1m count=1000 of=/dev/null
>    1048576000 bytes transferred in 13.766050 secs (76171160 bytes/sec)
>    1048576000 bytes transferred in 13.799268 secs (75987799 bytes/sec)
> 
> so 152 MB/s total rather than the expected ~238.  PCIe x1 slot is supposed to
> be good for 250 MB/s, so it ought to be able to max out both disks at once,
> or at least get close.

I have close numbers.

250MB/s is actually performance of the physical level. Logical level
also creates overhead of somewhere about 30-40 bytes per transfer. As
soon as most of desktop chipsets limited with 128bytes transfers, it
also shouldn't be forgotten.

The interesting fact I have seen yesterday, SiI3132 is able to read
150MB/s, but write 170MB/s. I am not PCIe expert, but looks like
transfer capabilities could be asymmetric. Also, and as soon as PCIe is
duplex, I've also seen 110MB/s read from one drive, plus 100MB/s write
to another, running at the same time.

-- 
Alexander Motin