Take a look in this interesting post of Dan MacAskill, CEO of SmugMug, about his experiences on OpenSolaris servers with ZFS and MySQL.
SmugMug is a digital photo sharing website, focused on professional photographers. The site is also famous for storing huge amounts of data (photos) using local filesystems and the Amazon S3 service. Just on S3 are 100 800 terabytes of data (according to this and this).
Very interesting pots because he tels in details his experieces over some diferents points of view.
Thanks for the link!
FYI, we’re well over 800TB now. :)