[CentOS] partitioning order and IO performance

Robert Nichols rnicholsNOSPAM at comcast.net
Tue Dec 22 23:13:55 UTC 2009

Carlos Santana wrote:
> Hi,
> Does mount point specification while partitioning (order in which I
> specify /, /boot, swap etc..) affect performance? I am not sure about
> the syntax, but I guess one can also specify address/block range while
> partitioning. Does it affect IO performance? Probably a stupid
> question, but just curious.. Any insights?

Not a stupid question at all.  For ordinary disk drives the answer is
yes, absolutely.  The outer tracks of a disk are physically longer,
and any but the most ancient of disk drives will pack more sectors
into those tracks.  Since the disk rotates at a constant RPM, more
sectors per second pass under the head on the outer tracks.  The
ratio of data rates for the outermost vs. innermost tracks is
typically 2:1 or a bit higher.  Add to this the need for more and
longer seeks for filesystems on the inner tracks (again, less data
on each physical track), and the performance degrades even more.

On most disks cylinder numbering starts at the outer tracks, but I
have heard of disks that number their cylinders in the opposite
direction -- never actually seen one, though.

Bob Nichols     "NOSPAM" is really part of my email address.
                 Do NOT delete it.

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