rmilner@zia.aoc.nrao.edu (Ruth Milner) (03/20/91)
In my next partition rearrangement, I would like to set up the most optimum
placement (physically) of partitions on the disk.
I am using SMD drives (Imprimis Sabers) and would like to know the following:
1. Given that there are a fixed number of sectors per track, is
there any difference in effective transfer rates between outer
cylinders and inner cylinders? I suspect not, or at least not a
significant one, since the outer cylinders revolve faster but would
have physically longer sectors. I believe (from something I read
in a disk manual long ago) that in fact this is one of the specifica-
tions of this type of drive: you get the same data rate to the heads
regardless of cylinder location. Please correct me if I'm wrong.
2. Despite point 1, it seems to me that there would be an advantage in
choosing either outer or central cylinders for the most frequently-
accessed partitions. Outer would be beneficial on a fairly quiet
system, since most of the time the heads would be at rest. (Here I'm
assuming that when they are at rest they go back to the outside of
the disk instead of staying where they were last; all of the drive
heads I have actually seen in action do this). But central would be
best on an I/O-bound system since that would give you the shortest
average seek from the previous position. So all I have to do is
monitor my system on an "average" day, or at least over some period
of time, and see what the disk I/O queues look like, right?
3. Is cylinder 0 the outermost on this type of drive?
If there is something glaringly wrong with my suppositions, or you can simply
think of a better way to do it, please let me know. Thank you.
--
Ruth Milner
Systems Manager NRAO/VLA Socorro NM
rmilner@zia.aoc.nrao.edu