Serial ATA and UDMA

James Wilkinson james at westexe.demon.co.uk
Wed Jun 30 12:16:38 UTC 2004


Edward wrote:
> Jonathan, I'm not sure about the controller itself, but don't forget a 
> lot of hard drives are still not really native UDMA/150. A lot are still 
> parallel hard disk drive interfaces 'converted' to a SATA interface. 
> PATA is currently at a limit of UDMA/133, so that may be what you're seeing?

And PATA is unlikely to ever go further...

Perhaps more to the point, you'll be doing extremely well to get more
than 60-70 MB/s out of the current generation of hard drives. IIRC, a
number of manufacturers are still on ATA100 simply due to this
limitation. 

OK, the cache / buffer memory on the hard drive can go faster, but this
is only of use if the hard drive is that much better than Linux at
predicting which data will be useful (normally reads that can be cached
will be cached in main memory by the Linux VM manager, so the hard
drive won't even be asked to provide them).

My advice? If you've got decent hard drive performance, be happy. If
not, something else is wrong.

HTH,

James.

-- 
E-mail address: james@ | NT is a one-legged cow, but even a one legged cow is
westexe.demon.co.uk    | fast when it's got 160+ rockets strapped to it.
                       | -- Nick Manka
                       | But that's not that impressive if all you can make it
                       | do is go around in circles. -- Darrell Fuhriman





More information about the fedora-list mailing list