Snapshot seems not to be ready to be used on a Network with Multisites and not even on Multisites as it saves a complete Mess.
Setting is a Network of Multisite Network
We tried to backup the network its self using the blog with ID 0 which has 4 IDs as sites inside that Multisite but their database does not get saved at all checking the log file, while their uploads folder does.
It results that the complete uploads folder get backed up no matter if it belongs to the site or not - actually it backed up all other sites belonging to this multisite even it forgets to beackup the database according to the logfile.
Snapshot does not offer any option to simply backup the complete stuff which would the most useful way doing that. It does also not offer incremental backups afaics.
Backing up another Multisite inside the network results in backing up only the database of the Network root but again not the subsites but all uploads folders of those subsites get backed up with all files.
The First Backup from site ID 0 took long and used 172 MB this is what gets displayed but it used actually 405.67 MB as this gets displayed in the backup results page! And again it is only backing up ONE site and not at all the complete Multisite!. This means for each single site in a Multisite Network you would need to setup the backup but that is simply not possible as the plugin gets only displayed on the network site.
The second from the first MultisiteID inside that Multisite Network used 198.99 MB which is quite strange as the Root ID does actually has no Media File linkes but the second site has media files links but those seem not to be backed up at all!
What backup solution are you using which also works on a Network of Multisites and also I would like to know what Backup really works reliable on Multisites at all.