filesystems - copy from NTFS to exFAT but "size on disk very" is very bigger than "size"

29
2014-01
  • Am1rr3zA

    I tried to backup from my NTFS external hard drive to new exFAT external hard drive when my copy finished I saw that I have very little free space remained. I checked my file size and I saw that the real size of my file is "30.4GB" but the size on disk is "396 GB".

    I must mention that number of file is so high (about 96110 Files, 10807 Folders).

    why this happened? how should I fix this? I formatted my new hard drive with exFAT filesystem with Allocation unit size of 4096 kilobytes.

    • Answers
  • week

    If my calculations are right than average file size on your exFAT is 331,7KB, but you've set minimal unit size to 4096 KB, which means that there is 92% unused space in every unit, so 96110 (files) x 3768,32 (freespace) = 362173235,2 KB = 345,40 GB (free) + 30,4 (real) = 375,8 GB, still missing few gigs somewhere, maybe because of that average size.

    In other words, set unit size as small as possible or use ".tar" or something like that.


    • Related Question

    osx - file size returned from ls - Linux vs OS X
  • dtlussier

    I have been moving a large number of files between a Linux system (ext3) and Mac OS X (HFS) and have noticed the slight variation in how the file size is reported by the ls command.

    Having done some digging round the man pages I'm guessing this difference has to do with how the actual data is stored on the disk, and/or how the ls command on each system is looking at the size (i.e. disk usage, blocks used, etc.).

    However, I'm still confused and wondering if there is a simpler answer to the different file sizes between the two systems. Is this a difference in the ls command, or in the filesystems? etc.


    • Related Answers
  • John T

    Likely it's the file system. The command is probably reporting a value as the size on disk rather than the actual size, and since each machine may be using a different cluster size, you see different values. More on the topic in this question.

    You can use tune2fs -l to see how your file system is currently configured.

  • Matt Garrison

    Which version of OSX are you running? Snow Leopard now uses base-10 calculations instead of base-2. If you're on 10.5 or older, I would attribute it to filesystems. Try comparing filesizes from a FAT32 thumbdrive.