A main NAS with 3 x 6 terabyte harddisks for storage in Raid (yields 12 Tb effective) with 3x1Gb SSD as cache to improve speed for recent used files. And a similar , bit cheaper NAS as backup without ssd cache capability, holding a weekly base, full backup but also incremental backups - if someone wants to retrieve a older version of a recently mistreated document ....
It is my second generation of NAS, the first 2Tb one did work well for 12 years but became slow for modern pc’s, the newer NAS-protocols are faster, new disks are faster and photo files are getting bigger when new camera sensor megapixels increase!
It survived 2 disk crashes without data loss thanks to Raid config, The older NAS used normal pc disks, less reliable than the newer server/NAS graded types.
It serves as storage server for 6 people-my family. Not only for photo but also for 6xpersonal storage (mail,work/University,contracts, tax records,....whatever) in 7 dedicated spaces (personal disks with access rights).
The photofolder is year---event-or-theme folder/subfolder based. It holds pictures since 1995 (the oldest are scans of film negatives).
Moving photo catalogs to an NAS - PentaxForums.com