Does HDD filling up really impact performance?

Discussion in 'MacBook Pro' started by rawdawg, Jun 29, 2010.

  1. rawdawg macrumors 6502

    Jan 7, 2009
    I've seen it here before where people say performance goes down significantly as your HDD fills up. Some explanations have been about the platters having lower read speeds as data writes towards the inside, but I've seen such claims rebutted.

    My new MBP is maxed out with RAM and I have multiple external drives. My internal is 500Gb and I've always worried about keeping it under 75% full, but if it's not necessary I would like to add my photos and music to it.

    Can someone please shed light on whether or not it effects HDD performance? (I'm not talking about when you have under 5Gb or even less available)

    Also, since I do heavy graphic and video work, is it important to have a scratch disk not on my media drive? My media drive is currently a RAID 0 I have hooked up via eSATA. I thought dedicated scratch drives are a thing of the past. Should I use my external FW800 (non-RAID)?
  2. Beefy macrumors member

    Jun 27, 2010
    Northern Colorado
    In my experience, yes.
  3. mrsir2009 macrumors 604


    Sep 17, 2009
    Melbourne, Australia
    No, I don't think so. BUT:

    When you save soemthing to the hard drive it takes up a block of data. Then when you edit it and save it again the new bit gets saved somewhere else. So when you open a file thats been edited multibable times, it will have to find ALL the data from DIFFERENT parts of the HDD.

    So its not actually filling it up that slows it down. Saving files and editing them lots causes THAT SINGLE FILE to slow down. NOT THE ENTIRE HDD.


    Not completely sure I'm right, but thats what I've heard!
  4. ljonesj macrumors 6502a


    Oct 20, 2009
    Kingsport TN
    yes i know with windows the page file expands and contracts to a certain amount if it needs unless u set it to use a certain amount to move stuff out of ram and vice versa i know in linux u have a swap partition i dont know how osx does with a page file or swap area but it could hurt it not have enought space on the hard drive

    ps just got in from work excuss the messy typing i am dead tired and cant type at the moemnt
  5. aeboi macrumors 65816


    Sep 20, 2009
    Bay Area
  6. tombilske macrumors member


    Jan 31, 2010
    mac uses HFS+ as it file system, and this eliminates the need for defragmenting the hard drive because it moves all of the blocks of data for one file so that they are together automatically. It cannot do this efficiently if there is less than 10-15% free space in the drive, and this results in fragmented files which means lower read/write speeds. so yes, it will impact on the performance of the drive if it is nearly full
  7. northerngit macrumors member

    Jul 16, 2007
    While this is somewhat true, there are other factors. HFS+ will only defragment files that are 20MB or less. If you have large video files, or VMware images, you'll find these fragment as badly as Windows NTFS.

    From a CNET article:

    A full drive will have a harder time finding contiguous blocks, leading, as the PP says, to fragmentation.

    Moreover, the inner platters of a drive are much slower than the outer ring. While block writes are random, the more near capacity the drive, the more often you'll hit this slower boundry.

    Of course, this point is mute on SSD drives.

    I've purchashed iDefrag and Drive Genius 3, both of which gave huge imporvments to performance on my MacBookPro - especially VMware.
  8. rawdawg thread starter macrumors 6502

    Jan 7, 2009
    Thanks for all the replies. Sounds like keeping the drive over 90% capacity wouldn't be a bad idea with all this in mind.

    Is there a way I could force my music to be on the inner portion of the platter? (Other than erasing and partitioning since I don't want to do that)
    If my drive is over half full now, if I were to toss in a bunch of video files so that when I add my music my drive would be full and then I go back and delete the video files to free up that space, would that force my music in the inner portion of the platter?

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