My storage/backup system is really, really simple but takes time to explain because of it's many levels of cascading backup. For the most part, each level is cloned by the level below it - data cascades down the chain. Dropbox is at the bottom not because it backs up everything above, but because it is just a small backup for important data and I didn't have a better place to put it. Crashplan is be the master of all prior data.
SSD + HDD. SSD holds preview files, catalog, etc. HDD holds last 3 months of shoots.
SSD is also cloned to matching sized partition on HDD every week in case of SSD failure.
External FW800 drives
HDD Dock, 2 2TB drives rotate with clones of last year of photos + catalog/preview. Rotated drive is held offsite every other month. My internal HDD is cloned to a partition on these drives.
4TB RAID 0. Holds ALL photos, catalogs, etc. The last 3 months are on here too as a 3rd backup (internal + docked HDD + this). Everything not in the last 3 months is referenced from LR to this drive. Feels as fast as my internal spinning drive, no problems with access speeds while editing.
UnRAID File Server
All files from all computers are backed up here along with media and photos. This is the FOURTH place my latest photos are stored, 3rd place that archive is backed up. Acts as media streaming server, file server, etc
Mac Mini Server
Used for email, web, internal projects, backs up catalog and preview files along with last shoot, and HTPC duties.
5th/4th backup location for my photos, more importantly it's off site. It also holds backups of everything on all machines.
Holds catalog file along with all kinds of other important data.