Hi!
Gingerale wrote:1) do checksums on partitions that are being moved or copied?
No.
2) most defrag programs do not touch metadata,
Metadata contains - among many other things - a list of sectors (counted from the beginning of the partition) that make up any given file, along with the order in which these sectors must be read. As a result, when moving data from one sector to another one (which is the basic building block of any defragmenting), metadata updates must take place - or you'll end up with 100% data loss. As a result, every defrag tool touches and changes your file system metadata!
That's correct - boot records reside outside the file system and are thus not touched by the defragging tools, since they are only interested in the space occupied by the file system.
and the like that are written (and invisible) in apparently "free" space. During a partition size reduction does Gparted relocate these items that could be in the way (i.e. in the middle of the free space)?
Anything that is recorded as present within the metadata is relocated, and the according metadata entries are updated. Anything not recorded will be left alone, overwritten, or simply not relocated before chopping off that sector from the partition - but this does nothing bad, since the metadata record are the only place where the contents of the file system are stored. Anything not listed in the metadata records is thus unknown to the file system - and will eventually be overwritten while the file system is allocating new blocks for a file, since nobody knows that stuff is there.
Here's an attempt of including an image of what Perfect Disk defrag program had to show in the available space:
Anything listed in this screen shot as "occupied" (that is, non-white block) is recorded in the file system metadata area and will thus be relocated during resizing. However, these blocks might me marked as e.g. "excluded" by your tool since they are
- either defective (the file system metadata records them as unusable then, and GParted can take care not to use them while resizing. I don't know if it actually does this - maybe one of the developers can help you here!);
- or occupied by files that Windows currently holds open (paging file, registry, ...). This won't be a problem either, since there will be no running Windows while GParted is being used.
I noticed that this screenshot also lists some "metadata" blocks, but also holds several "MFT" blocks. This means that this tool makes a difference between the MFT on a NTFS partition (this data structure records which file is stored where, which access rights apply to any given file and so on) and "other" metadata.
In contrast to this, I called anything that is not your user data or a directory as "metadata" - as a result of this, I'd simply include the MFT in the "metadata" area.
Unfortunately, this term is not so clearly defined...