sorry for the late response - I was quite busy this week.

as you said sequential i/o will be re-blocked by the kernel to 64k chunks.
would it be possible to dynamically resize this value by the vm?
(alternatively, is it possible to increase this value by hand?)

some tests, as usual:

NetBSD-1.5Y, all of these are "first-run" tests. (same disk, same machine,
same partition layout, etc.)

# time dd if=file1 of=file2 bs=64k count=1024
	38.60s real	0.00s user	1.36s system

# time dd if=file1 of=file2 bs=1024k count=64
	12.97s real	0.00s user	1.36s system

# time dd if=file1 of=file2 bs=8192k count=8
	11.10s real	0.00s user	1.32s system

and then the same tests on Linux 2.2.19:

# time dd if=file1 of=file2 bs=64k count=1024
	8.45s real	0.00s user	1.54s system

# time dd if=file1 of=file2 bs=1024k count=64
	8.50s real	0.00s user	1.55s system

# time dd if=file1 of=file2 bs=8192k count=8
	8.75s real	0.01s user	1.65s system

sorry, there are no FreeBSD test results this time due to a hardware
failure.

--
Gergely EGERVARY
System Administrator
Business Polytechnic, HUNGARY