difference between size and size on disk?

[leaaaa]

i have been wondering for a while now what is the difference between the size and size on disk in the properties of a file.

[Chris]

The file [example] is 2.5KB [2,716 Bytes].

Now on your disk you will have a cluster size, the cluster size by default is, 4KB [i think] The whole of that cluster will be used. So whilst the file is 2.5KB the whole cluster will be used for that file. So 4KB is really used and wasted in a way.

But this is a very small file size and makes more sense when you look at larger files.

[djohn]

This is an interesting article, (extract below) that explains the best way to obtain maximum storage space from your drive. lost me on the first page though! :blink: Here

When a file is stored on a disk, it’s written into clusters. If the file being stored exceeds the cluster size allocated to it, the file system uses additional clusters to store the file, consuming clusters until the file is stored. Naturally, files almost never fall neatly into multiples of 4 KB. So when the file system uses additional clusters, the unused portion of the last cluster is lost to overhead.

For example, suppose that you have a 35-KB file on your hard disk. The largest cluster size available is 4 KB. Therefore, the file will use a total of nine clusters. Eight of those clusters will be a full 4 KB in size. The ninth cluster will contain only 3 KB of data, leaving 1 KB completely wasted. If you had to store a thousand 35-KB files, you’d lose 1 MB of drive space.

[Chris]

:D

[leaaaa]

thanks a lot. :-)