Clarification on usage of Volume Shadow Copy

When we use --use-fs-snapshot does restic uses VSS only for files that are locked or it uses VSS for every single file?

The problem is I don’t trust the machine to have enough available space to use VSS on every file (I have files that are hundreds of GB) but I would like to enable that so it can backup locked files that I know will be small or at least not as big.

Check here for a description of what VSS does: Volume Shadow Copy Service | Microsoft Learn

As I understand it, services collaborate to create a consistent snapshot. Only files that are written after the snapshot is taken might be copied, if the respective service does not support writing deltas. So the answer to „do I have enough disk space for a backup using VSS?“ is: It depends.

a snapshot is done at the block level, not file level.

to create a snapshot, read from it and then delete the snapshot, uses little to no extra space.

i am a very heavy user of vss snapshosts.
have my own approach to creating the vss snapshots, so i do not use restic vss functionality.

that way i can use vss with veeam, rclone, 7zip, fastcopy and now testing with restic.

takes just a few lines of simple batch .cmd