Ddiskrices.com crawls amazon data. Has filters, shows price per GB/TB, makes for a really good tool to find storage at good prices.
Serverpartdeals.com sells recertified/ refurbished Enterprise drives that were usually used in data centers. Makes for much cheaper drives that usually come with a warranty, but i'd advise going this route only if you're working on a RAID system and have spare money to be able to quickly replace drives in case of failures.
Backups on installgentoo.com
Data recovery on installgentoo.com
Data destruction on installgentoo.com
Only semi-related, Home servers on installgentoo.com
Don't forget the 3-2-1 backup strategy; 3 copies, 2 on different types of media, 1 offsite.