Sync for mobile devices has a special "Backup" function. Technically, backup adds a folder on a mobile device and shares a Read Only Key. However, there is one major difference between a regular Read Only share and a backup: if any data gets deleted from your mobile device, it is not deleted from the peers who possess the backup Key. It means that your backup computer is going to accumulate Pictures / Music / whatever data you decided to backup. @kkxxxxxxx 是正确的