I know, I was speaking about physical platters of course. Mark Hann told
me in private that he disagreed with me, so I checked recent disks (36, 73, 147 GB SCSI with 1, 2, 4 platters) and he was right, they have
exactly the same spec concerning speed. But I said that I remember the
times when I regularly did this test on disks that I was integrating about
7-8 years ago, they were 2.1, 4.3, 6.4 GB (1,2,3 platters), and I'm fairly
certain that the 1-platter performed at about 5 MB/s while the 6.4 was around
12 MB/s. BTW, the 9GB SCSI I have in my PC does about 28 MB/s for 1 platter,
while its 18 GB equivalent (2 platters) does about 51. So I think that what
I observed remained true for such capacities, but changed on bigger disks
because of mechanical constraints. Afterall, what's 18 GB now ? Less than
one twentieth of the biggest disk.
Anyway, this is off-topic, so that's my last post on LKML on the subject.