1.    25 Jan 2016 #1
    Join Date : Dec 2015
    Posts : 6

    Hard drive cluster size issues? Size on HDD over twice the actual size

    I went to SSDs on all of my computers some time back, but I still use WD RE4s and 2.5 inch WD Black HDDs for a variety of backup tasks and for storage in which the data will not be accessed for a period longer than is ideal to use a non-powered SSD for. On my Macs I am using El Capitan with OS X Journeled, GUID map, and FileVault 2 encryption. On my SP3 and desktop I am using NTFS with Win 10 64-bit Pro with BitLocker enabled on both machines. The OS and third party programs are currently up to date.

    I've generally used ExFAT and the GPT partition map because it allows me to use it on all of my computers, and I have always used the default cluster size. However, I do not think the default size was the best decision for me because the size on disk is over TWICE the actual size.

    If I am correct, the default Win 10 cluster size is 4k, and that going BELOW that is useful for the drives I have many smaller files on. Is this correct? Additionally, the smaller cluster size I go, the slower the drive will write, correct? Also, if so, how low do you advise going? I am still torn between reformatting outright or trying one of the programs that allows changes to a currently in-use drive. Any advice? Thanks!
    Attached Thumbnails Attached Thumbnails Capture.PNG  
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  2.    25 Jan 2016 #2
    Join Date : Jul 2015
    Posts : 2,552
    10 Pro

    For the a sector size of 4k to double your disk utilization you'd have to have a really tiny average file size. From your numbers shown the average size if I calculate it correct is 132kb (unless you have 1 massive file and 17,711 tiny ones) so a 4k size will make no difference.

    You could check with TreeSize Free - it will tell you if you right click on the status bar and select it to be displayed.

    Click image for larger version. 

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    EDIT - having checked the default for ExFat is 128k for drives over 32GB (https://support.microsoft.com/en-us/kb/140365) and when I tried to format an external USB drive that is what it picked. According to macbook - Reformat exFat with specific Device Block Size and Cluster Size - Ask Different OSX picks 128k also.

    So if you had 128k as your cluster size minimum disk utilization would be 17,772 files * 128k = 2.17GB. So if all your files were just over this (say 132k which looks like your current average size) you would be using 4.44GB add a couple of big files and it could easily be 6GB.

    I would check your average file sizes and also your current cluster size (you can use chkdsk as described in the AskDifferent link above).

    The default is 4k for NTFS and I have always formatted ExFat as 4k also. Depending on your current setting reformatting 4k looks like a good idea.

    As for how - copying the data elsewhere, formatting and then copying it back has to be the easiest, safest and most likely fastest way. You'll also get the disk defragmented automatically. There are tools to do it but they seem to have limitations and I wouldn't bother if you have a spare disk.
    Last edited by lx07; 25 Jan 2016 at 05:12. Reason: Perhaps setor size <> 4k
      My System SpecsSystem Spec

  3.    25 Jan 2016 #3
    Join Date : Jul 2015
    Posts : 2,552
    10 Pro

    If you like this lets you change cluster size and is free if you download it within the next day.

    MiniTool Partition Wizard 9.1 Pro (100% Discount) - Windows 10 Forums
      My System SpecsSystem Spec


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