SATA question

[Andy Burns]

Ivan Gyurdiev wrote:

> I'm confused... is my sata drive (ata3 below) running at the proper speed?
> This is a western digital SATA 2 drive. The messages below mention both  
> 3.0Gbps and UDMA/133, which I don't understand.

You're seeing the similar messages that I do, the controllers seem to be 
recognised as 3Gb/s but the drives are either reporting or being 
recognised as 133MB/s

in my case the drives (WDC WD2500KS )are *not* PATA drivers with 
on-board SATA bridge chips, how about yours?

> hdparm -I says udma6 is being used.
> Testing my old drive, with this new SATA II one shows very similar 
> performance,  near 60MB/s (via hdparm -Tt). Is this unusual? I would 
> expect some kind of improvement...

Again that's about the same speed as I get

# hdparm -t -T /dev/sda

/dev/sda:
  Timing cached reads:   4456 MB in  2.00 seconds = 2229.43 MB/sec
  Timing buffered disk reads:  180 MB in  3.02 seconds =  59.61 MB/sec

and that seems to be sustained during mdraid rebuilds rather than just 
on the small test that hdparm.

What does hdparm -T show? If it shows above 1.5Gb/s then at least your 
physical interface is doing the SATA II speed to the drives,

Not that this is going to improve real world performance much as you 
already saw the physical disk transfer tops out at 60MB/s which is 
"only" just over 0.5Gb/s

so in my case the interface between motherboard and disk electronics is 
37 times the speed of the interface between disk electronics and disk 
surface, sata II's 3Gb/s speed is irrelevant, if only I had NCQ that 
could make a difference ..