SharePoint 2016 - How to archive the my unused sub-sites

Question

I've a SharePoint 2016 Farm, in a Site-collection I do have many sub sites, which are currently not in use. So i want to Archive them to reduce the space.

what is best way to archive the sub sites ?, I'd like to save them as a single file and whenever we need them, we will extract it and work with them.

Note that the sub sites has unique permissions, and has lot of documents and custom pages. Hence their size exceeds 50MB. so we want a better solution than saving the site as a template.

Answer 1

If you need to save unique permissions, per my knowledge you will need to use some 3rd party tools. Export-SPWeb does not contain unique permissions neither.