How to connect to Synology NAS with different account? example, TimeMachine vs admin

I was trying to setup TimeMachine backup to my Synology NAS. I used to have USB-HD worked fine. However, followed the instruction http://forum.synology.com/wiki/index.php/Backup_Mac_data_using_Time_Machine I always have a "backup failed" message, even I can access the TimeMachine folder on NAS from Finder.






Anyone have idea?

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Problem solved: I deleted the USB HD Time Machine choice, only use the NAS, then backup works!
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One more simpler question:
Can Mac to connect to NAS with different accounts at the same time? For example, mount a TimeMachine from NAS with "tm" account, at the same time, mount "Photos" from NAS with "admin" account.