If files present in a PC backup are also present (previously or subsequently) in a WHS shared folder, does this use up 2 lots of server space (saving the file twice with 2 independant copies, wasting space), or is the 2nd instance of each file linked to the first, making (I assume) considerable file space savings?
As I hinted above, maybe the order matters too - PC backup copy before or after shared folder copy?
Files in question are not so big - photos - but many of them.
The PC Backups and the Shared folders are fully separated entities in the context of storage use. Single instance storage is refering only to files, which are appearing on several PCs in your network - identical clusters of those will only be hold one time in the backup database.
For fotos I recommend to use a shared folder with duplication enabled and perform regulary backups to external drives (of which at least one should be stored outside of your home due to avoiding total loss in case of catastrophic events hitting your home).
The PC Backups and the Shared folders are fully separated entities in the context of storage use. Single instance storage is refering only to files, which are appearing on several PCs in your network - identical clusters of those will only be hold one time in the backup database.
For fotos I recommend to use a shared folder with duplication enabled and perform regulary backups to external drives (of which at least one should be stored outside of your home due to avoiding total loss in case of catastrophic events hitting your home).
I'm already doing as you suggest, working from the shared folders for photos. It's probably still wise to keep files included in PC backups until put into shared, duplicated, backed up storage. Yes, I do a regular backup which is taken offline and down the garden!