Do partitions correspond to physical locations on a disk?

Discussion in 'Mac Basics and Help' started by AmbientChaos, Jul 4, 2014.

  1. AmbientChaos macrumors member


    Feb 11, 2014
    So I'm splitting a disk into two partitions for use with Mac and Windows: the Mac partition is just general data storage while the Windows side will hold Steam games that don't fit on my SSD.

    Anyway, I was wondering if partition 1 or 2 will have performance differences.

    For example, here is a picture of a currently partitioned disk, Mac partition first then Windows.

    If the Mac partition is the first partition, and a file was copied to it immediately following partitioning so it is on the outermost and fastest rotating part of the disk, would it not stand to reason that an identical file copied to the second partition will suffer from slower read times as it is the same size but the disk requires more rotation to read the same data? (included picture of disk rotating)

    If partitions do correspond to physical locations, then reading the first file on the first partition will be faster than, the last file on the first partition, which would both be faster than any file on the second partition?

    tl;dr copying files to multiple partitions and was wondering if strategically placing files on different partitions of the disk will affect how fast data is read to/written.

    sorry if this is a bit unclear. I haven't been able to find any information of the sort on the internet. Maybe I wasn't using the correct search terms but I still couldn't find anything
  2. mfram macrumors 65816

    Jan 23, 2010
    San Diego, CA USA
    Yes, in general, your assumption is correct... but with caveats. The operating system talks to the drive using "logical blocks". The internal drive electronics are responsible for mapping between logical blocks and physical locations on the disk. There are cases where the data might be re-arranged a little bit. For example, because of impurities on the disk, some areas might be re-mapped to replacement blocks. I would suspect in the case of re-mapping the disk would try to choose an area close to the original area, but that may not be the case.

    And, of course, none of this applies to SSDs. Well, at least not in geometry you've described. There are going to be totally different factors at work in SSDs.

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