Low HDD tranfer rate with FreeBSD 5.3-Release

[Dan Nelson]

In the last episode (May 09), Eric Anderson said:
> > Eric Anderson wrote:
> >> Amandeep wrote:
> >>> I am using Tyan S2098 MB with 160GB Maxtor ATA  Drive and the
> >>> transfer rate is very low. FreeBSD 5.3-Release.
> >>> Any ideas what is going on here.
> >>>
> >>> The transfer rate is about 15MB/s
> >>>
> >>> when I run
> >>> #dd if=/dev/zero of=/usr/junk bs=8192
> >
> >Shouldnt it be around 54MB/s for a regular IDE drive.
> 
> What about other block sizes?  Also - you should paste your actual dd
> output here too.
> 
> What's the model number of that drive?  Maxtor claims (on one of
> their 160G drives) 17.8MB/s from inner diameter disk and 35.6MB/s for
> outer diameter for the 5400rpm drives.

Yes, try 64k instead of 8k, and also compare read speeds.  If you have
the time (could take an hour or so), try "dd if=/dev/ad0 of=/dev/null
bs=64k", run an "iostat 60" in another window, let the dd run through
the entire disk, and compare the relative speeds from start to finish.

For the DiamondMax 160, the sustained throughput should be 26MB -> 50MB
as you go from inner to outer tracks.

-- 
	Dan Nelson
	dnelson at allantgroup.com