Backing up files on a volume that utilizes the new NTFS deduplication functionality will fall into one of two categories, optimized and non-optimized. Deduplication aware applications, such as Windows Sever Backup, will backup files in their deduped (aka optimized) state. While older backup programs will not understand the layout and backup the files in a non-optimized state.
Performing an optimized backup results in a smaller, faster backup. The backup is smaller because the total size of the optimized files, non-optimized files (files that are not included in policies), and data deduplication chunk store files are significantly smaller than the full logical size of the volume (that is, the size of all the files before deduplication). Optimized backups are faster because there is less I/O and because the optimized files are not restored/rehydrated during the file copy operations. Selective backup (in which most of the volume is being backed up) may also benefit from using the optimized backup approach if the logical size of the selected files is significantly greater than the physical size of the optimized files plus the chunk store container files.
In non-optimized backup and restore, the backup application does not use the Data Deduplication backup and restore API. Instead, the backup application opens the files and copies them without specifying the reparse point flag.
The optimized files are coped to the backup volume as normal files, not as optimized files. The conversion from optimized files to normal files is performed transparently in memory by Data Deduplication when the backup application copies the files. Restoring from such a backup store is a normal file-copy operation.
The size of the data in a non-optimized backup is normally much larger than the original optimized volume because of the space savings that is provided by deduplication. A full volume restore from a non-optimized backup will usually not fit on the original or an equivalently sized volume.
Non-optimized backup is normally used only for the following situations: