Synology NAS

[Enquiries]

I need a NAS rack setup for file backup, massive video and picture backup, Plex server, vpn setup, and access and upload from anywhere in the world. I am looking for a 8-12 Bay Synology NAS rack station and came across the RS2423RP+. I want to begin with a RAID setup that will begin with 4 of the WD Red Pro 18TB drives and then add additional drives to the Raid 6 config later. Can that be done without losing data on the initial raid setup? I am wanting Raid 6 to account for two failed drives if that ever happens again…trying to be safe this time. Also, does Synology software have a feature for full daily backup to cloud service? If not, can you please recommend a cloud service? Please let me know your thoughts about my planning above. Your expertise will be much appreciated. And, thank you for all of the great videos on YouTube. They are extremely helpful and your knowledge is surpassed by none.
Thank you.
Sincerely,
Shahzad Qadri