On Wed, Jun 27, 2007 at 08:40:58PM +0200, Jukka Salmi wrote:
> Jukka Salmi --> netbsd-users (2007-06-26 17:05:25 +0200):
> [...]
> > Hmm, any hints what could be the bottleneck here?
> 
> I've done some more rough testing to compare SATA vs. PATA read and
> write speeds on wd, ccd and raid (levels 0 and 1), to and from the raw
> devices and ffs respectively. I used dd(1) to write (read) 1 GiB to
> (from) the device. The results are in MiB/s as reported by dd:
> 
> 
>                         |-- SATA --|    |-- PATA --|
>                         read   write    read   write
> 
>         wd:      raw      50   39         36   36
>                  ffs      50   42         36   36
> 
>         ccd:     raw      91   40         72   72		
>                  ffs      92   45         71   72				
> 
>         raid 0:  raw      90   40         71   73
>                  ffs      90   45         68   70
> 
>         raid 1:  raw      49   21         35   36
>                  ffs      49   23         35   36
> 
> 
> Of course dd(1) is not a benchmark, but the results are - at least to
> me - quite surprising: while read and write speed are always almost
> identical on the PATA devices, reading from SATA devices is much faster,
> but writing to them is much slower. Hmm. Not quite what I had expected.
> I'd check with another sata controller if I had one...

Note that this can also be dependant on the drives. 
The attached program will test the bandwidth between the drive's cache and the
host. usage: ./tst /dev/rwd0d 10000 (increase last parameter if it completes
too fast to give accurate results).

-- 
Manuel Bouyer <bouyer@antioche.eu.org>
     NetBSD: 26 ans d'experience feront toujours la difference
--