USB stick capacity

Discussion in 'macOS' started by ggulliver, Jan 27, 2016.

  1. ggulliver, Jan 27, 2016
    Last edited: Jan 27, 2016

    ggulliver macrumors member

    Jan 22, 2008
    This isn't a Mac issue, but unsure of where (and indeed whether) to post, here goes...

    I'm sure many are aware of the issue of USB sticks being advertised as greater capacity than they are.

    I'm aware of the various tests - which often take many hours to confirm initial suspicions - and no longer bother to run them. Instead, I'll just write music files to them and then see what plays back ok - things usually screw up below 8gb, and that's much quicker than the write and read tests.

    In a couple of instances, when viewing the items in Disk Utility, their capacities are shown as a few gig more than the supposed capacity... which immediately seems odd (I've understood the available should be less than the advertised capacity) and I'm wondering if this is a reliable initial indicator (or not).

    And, with one which arrived this morning, CarbonCopyCloner showed an alert message of something like 'not enough room, capacity is only 4gb' (on what should be a 64gb stick) - so I'm wondering about that too... because at the moment it appears to be reading beyond that 4gb. (Update - it seems to fail at about 8gb.)
  2. Fishrrman macrumors G5


    Feb 20, 2009
    Important question:
    How is the USB flashdrive in question formatted?

    Mac format (HFS+), or something else?
  3. JohnDS macrumors 65816

    Oct 25, 2015
    What format is the USB stick formatted in? It sounds like it might be formatted as FAT32. FAT32 has a limit of 4 Gigs for a single file.
  4. ggulliver thread starter macrumors member

    Jan 22, 2008
    It's Fat 32 - but that shouldn't affect the indicated size of the entire stick.
  5. JohnDS macrumors 65816

    Oct 25, 2015
    It won't. But the error message might have meant that CCC was trying to copy a file larger than 4 GB. Either that, or CCC was trying to make a disk image and the image file was larger than 4 GB.

    What is it you are trying to do anyway? If you are trying to make a bootable clone, you need to reformat the stick as Apple Extended Format (Journalled) anyway.
  6. ggulliver thread starter macrumors member

    Jan 22, 2008
    CCC was simply trying to clone - and no files are larger than about 20meg.

    And 'what I'm trying to do' is outlined in the initial post... write files to a usb stick to determine if the capacity of that stick is genuinely as described or lower.
  7. JohnDS macrumors 65816

    Oct 25, 2015
    Are you sure CCC wasn't trying to clone a hidden file, like a Spotlight index for instance?

    If all you are trying to do is to check the size of the flash drive, why use CCC? Just use drag and drop from Finder.

    Anyway, the difference between advertised and actual disk size is usually because the manufacturer advertises the disk size base on 1,000 bytes = 1 KB, whereas formatted size is based on 1,024 Bytes = 1 KB. See:
  8. ggulliver thread starter macrumors member

    Jan 22, 2008
    No, it wasn't trying to clone anything hidden.

    I use CCC to transfer because finder drag and drop is often slow and can hang the Mac. Plus, using CCC the process can be paused/stopped/resumed.

    And that link to capacity info states what I'd outlined in my initial post - that 'available' should be LESS than the supposed capacity of the stick, not more... and that if it's more it suggests a hokey stick that's been interfered with to show a capacity greater than actual.

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