Technically, tertiary storage is realized by tape drives and magnetic tapes, by tape libraries, Automated Tape Libraries( ATL), RAID systems and RAIT systems. Storage capacities are in the range of petabytes (`10^15`) and exabytes (`10^18`).
Tertiary storage gets its data from secondary storage and can store it for years and decades. The advantage of tertiary storage over primary storage and secondary storage is the low cost of a storage unit. The disadvantage is that access times are in the range of seconds and minutes.