"size" vs "size on disk"?
"size" vs "size on disk"?
Hello everyone, I’m trying to move a folder from my NAS to my local machine using a script. The properties window shows both size and size on disk, but I’m not sure which one matters more. On my system, 144GB should fit comfortably, while 11.4TB seems impossible. Can someone clarify the difference between these values?
Most NAS devices include compression enabled by default, meaning the stored file sizes reflect compressed data. I initially thought the numbers indicated 11.4 GB instead of TB, which likely caused confusion. Updated: I suspect snapshots might be active and frequent file changes could be contributing to this issue. Edited October 18, 2021 by RONOTHAN##
I tried to cover it all on my own, though my translation abilities aren’t great. Here’s the full info from the link you shared: https://askanydifference.com/difference-...e-on-disk/
Size refers to the true dimensions of the file. Disk space is how much room it takes on the storage device. This depends on the disk's grouping capacity. For instance, with a 4KB group size, a single byte file must be at least 4KB because that’s the smallest addressable chunk your drive can use. The big variation suggests the drive was tuned for big files, possibly using a large group size but holding many small ones.
Various factors influence how files appear in size, often causing discrepancies between total storage used and actual file dimensions. Physical limits of storage may also play a role. External links or references to files can affect space usage depending on the underlying filesystem. The same file might be stored multiple times, increasing its footprint. Additionally, some systems allow several streams per file, which can lead to unusually large allocations for certain streams.
Many responses are overwhelming! I’m trying to understand how the file system affects these results. When moving files locally, the disk size should match more closely with the actual size. @Eigenvektor tried a small text file and got 256MB on disk—seems accurate. @HanZie82 your note is useful. @RONOTHAN your question about snapshots is important; they can explain storage differences. @porina regarding references: if a file is used three times, does it really double the storage? I’m still trying to grasp what you mean by streams.
I don't know how smart or stupid file explorer is, but there is some risk it might count multiple times.
It seems unlikely there are 256MB clusters; the NAS might be returning incorrect data. In this scenario, I’d skip the "size on disk" information.