"Size on disk" means what? OneDrive clarification

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  1. Kari's Avatar
    Posts : 16,159
    Windows 10 Pro
       #11

    Difference between actual size and size on disk has nothing to do with compression.

    Default Allocation Unit (AU) size on an NTFS formatted disk is 4 Kb (4,096 bytes):

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    One AU can only contain data from one file. Any unused space in an AU will be lost, it can't be used to store data from another file. A file from 1 up to 4,096 bytes uses one AU, a 4,097 bytes file requires two AUs, and so on.

    Theoretically, if a data disk is only used to store small files, you could save some disk space by selecting a smaller AU size when formatting. In reality, the possible disk space saved would be meaningless, thinking of todays SSD and HDD sizes.

    If your data drive is used only for extremely large files like for instance HD TV shows and movies, you might gain a little better performance using larger AUs, because Windows would need to go through less AUs when you play the movie. But, again, the difference would be practically unnoticeable.

    An example. In screenshot properties of a small Word document:

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    The file is 22,692 bytes. On disk, it requires 6 AUs (6 * 4,096 = 24,576 / 24 Kb) because it is 2,212 bytes too big to fit in 5 AUs (5 * 4,096 = 20,480). In other words, this last 2,212 bytes of the file is stored on last AU. The rest of this AU (1,884 bytes unused space) cannot be used to store data from any other file, file system marking the whole AU reserved.

    Kari
    Last edited by Kari; 14 Jul 2019 at 10:47. Reason: Fixed some typos
      My ComputerSystem Spec


  2. Posts : 452
    Windows 10 Home 64-bit and ANDROID Lollipop
    Thread Starter
       #12

    Thanks for the technical detail. I am not sure how it relates to my issue, which is basically that I have been unable to reduce the amount of space taken by One Drive. I t remains at Size 16.7 GB, Allocated 14.9 GB, whereas I think it should be closer to zero. I have just spent several hours manually making files 'Online only' and in some cases 'Keep online' without it having any effect on the space consumed. Have I done the right thing? What is the difference between 'Online only' and Keep online' if there is one? I presume I am correct in assuming that 'online only' means not on my computer (though available from it.)?

    Having now only 5 GB free after 7 GB disappeared I want to get this sorted out, before attempting the current update (though I understand it can still be done --- as before --- with the help of an external drive.)
      My ComputerSystem Spec


  3. Posts : 452
    Windows 10 Home 64-bit and ANDROID Lollipop
    Thread Starter
       #13

    Further to my post above about my One Drive not having space saving (and other) options in Settings the snip below shows the only Settings which are displayed in my One Drive app
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      My ComputerSystem Spec

  4.    #14

    I do not know for sure, but it is entirely possible (and reasonable) that the 'online' settings won't remove a file already on your local system. So try Wiztree to confirm what is actually on your local drive, then (as long as the files are known to be online, and preferably backed up somewhere else), try removing the local copies.
      My ComputerSystem Spec


  5. Posts : 452
    Windows 10 Home 64-bit and ANDROID Lollipop
    Thread Starter
       #15

    I think I may have found the, or at least one, cause of the problems. I do not have, and suspect I never have had, the OneDrive Action Centre with is access to settings / options on my OS. It may be that it was missed out of the update that introduced it a while back, or is present but not enabled. I see there is a way to enable it using a reg edit. This is something I generally avoid as it is not something I am confident to do. I am awaiting a response from MS Support.
      My ComputerSystem Spec


  6. Posts : 452
    Windows 10 Home 64-bit and ANDROID Lollipop
    Thread Starter
       #16

    That should read Activity Centre not Action Centre. It seems this might be solved by RESETTING or UNINSTALLING OneDrive. I need to be sure that neither of these will wipe out what I have installed in OneDrive. I am not sure whether there is a risk with this as what is stated seems unclear and contradictory.
      My ComputerSystem Spec


  7. Kari's Avatar
    Posts : 16,159
    Windows 10 Pro
       #17

    clayto said: View Post
    Thanks for the technical detail. I am not sure how it relates to my issue.
    I am sorry if you did not understand my reply, sorry that I answered your question. You asked a specific question "Size on disk" means what?" in your thread title. I answered that exact question, and you were unhappy with my answer. It's like asking what's 10 times 10, and when someone answers it's 100, you would say that you did not want to know how much is 10 times 10.

    Next time, I try to remember that when you ask something, you do not want an answer to that question.

    OneDrive Files on Demand feature works. If you have any issues with it, see the tutorial: Turn On or Off OneDrive Files On-Demand in Windows 10

    You can turn it on or off as you wish:

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    Kari
      My ComputerSystem Spec


  8. Posts : 452
    Windows 10 Home 64-bit and ANDROID Lollipop
    Thread Starter
       #18

    Thanks for displaying the menu above (Settings etc) because it has confirmed what may be the core of the problems, which is that I do not have that menu on my system! It is the first time I have seen it, and I have not discovered any way to bring it up despite repeatedly clicking everything in sight. I am sure now that OneDrive on my PC is corrupt or at least partly missing, or perhaps there are features present but not enabled. As a result I am now in correspondence with a Support tech from a dedicated OneDrive service and hopeful that we will soon have it working correctly..
      My ComputerSystem Spec


 
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