SATA 300 Drive Being Run At 150

[Dan Nelson]

In the last episode (Jul 21), Tim Daneliuk said:
> I asked this question a while back, but needed to do more digging to make
> sure I had latest sources etc.
> 
> I have an Intel motherboard that shows this for a SATA controller:
> 
> atapci1: <Intel ICH7 SATA300 controller> port 0x20c8-0x20cf,0x20ec-0x20ef,0x20c0-0x20c7,0x20e8-0x20eb,0x20a0-0x20af mem 0x90204000-0x902043ff irq 19 at device 31.2 on pci0
> 
> But the hard drive - a SATA 300 device - shows up like this:
> 
> ad4: 238475MB <WDC WD2500JS-00NCB1 10.02E02> at ata2-master SATA150
>                                                             ^^^^^^^
> Using dd, I have confirmed that the drive is running nowhere near
> SATA-III speeds, at least on reads:
> 
> 968470075 bytes transferred in 7.132891 secs (135775249 bytes/sec)

What was your dd commandline?  If you've got more than 1GB of RAM and
tested by reading a file and not the raw device itself, you just tested
FreeBSD buffer cache. According to
http://www.wdc.com/en/products/productspecs.asp?driveid=135 , that
drive's maximum sustained speed is only 93.5 MB/sec, so it doesn't
really matter if your interface is running at SATA150 or SATA300 unless
you plan on reading exclusively from its 8MB buffer :)

-- 
	Dan Nelson
	dnelson at allantgroup.com