vinum and newfs

[Mike Maltese]

What impact do disk block and fragment sizes have on a vinum volume?  I've
been benchmarking an array of three drives in striped and raid5
configurations with various stripe sizes.  I've noticed that I get better
results in just about every instance by passing -b 16384 -f 2048 to newfs.
This doesn't make sense to me as those are the defaults for newfs if they
are not specified, but looking at the disklabel after a newfs, it shows
8192/1024. Should these options really make a performance difference, and if
so, how?

Thanks, Mike