In reply to a post by matty_hunt:

Also did a defrag with Defraggler. First run and the disc free space dropped from 449Gb to 341Gb.

Defragging should not alter disk free space. It just moves things around so that files are more contiguous.

In reply to a post by XRaySpeX:

Defragging should not alter disk free space.

Depends. If 1000 1K fragments each take up a 64K block, that would 64 Meg of space. If all jiggled together, that would be about 1 Meg.

Ok, so it's not that simple, but defrag does change disk space usage if dealing with lots of small fragments.

Doesn't work like that!

All the blocks/clusters on a disk are of equal size, in your example 64K or on my XP NTFS disk 4K:

Which drive to read [A-Z]? C
Windows NT v5.1, Build=2600, ServicePack=Service Pack 3
C: Sectorsize=512, BlSize=4096(8) , Sectors=367296K, Blocks=45912K, Free=40132K

, each made up of an integral # of 512B sectors.

Multi-sector blocks are used to keep the disk addressing manageable on an enormous disk.

You don't have fragments that are smaller than a block. Fragments are not small blocks but are blocks of a file that are separated from other blocks of the file on the disk. Defragging attempts to put them all together.

Think you are confusing it with, e.g, that a small 1K file uses up a whole 64K block, or the usual example that a 1 byte file takes up a whole 64K block. There is nowt you can do about that; small (< 1 block size) files will always waste disk space as will the last logical block of any larger file.

Edited by XRaySpeX (Fri 18-Apr-14 15:40:10)

You're correct on that one, however, defragging often does alter disk space because as a side effect it causes shadow copies to be purged, which in turn often frees up disk space.