Storage Hierarchy (Cont.) primary storage:Fastest media but volatile(cache,main memory). ■ secondary storage:next level in hierarchy,non-volatile,moderately fast access time Also called on-line storage E.g.,flash memory,magnetic disks tertiary storage:lowest level in hierarchy,non-volatile,slow access time also called off-line storage and used for archival storage e.g.,magnetic tape,optical storage ·Magnetic tape Sequential access,1 to 12 TB capacity A few drives with many tapes Juke boxes with petabytes (1000's of TB)of storage Database System Concepts-7th Edition 12.4 ©Silberscha乜，Korth and SudarshanDatabase System Concepts - 7 12.4 ©Silberschatz, Korth and Sudarshan th Edition Storage Hierarchy (Cont.) ▪ primary storage: Fastest media but volatile (cache, main memory). ▪ secondary storage: next level in hierarchy, non-volatile, moderately fast access time • Also called on-line storage • E.g., flash memory, magnetic disks ▪ tertiary storage: lowest level in hierarchy, non-volatile, slow access time • also called off-line storage and used for archival storage • e.g., magnetic tape, optical storage • Magnetic tape ▪ Sequential access, 1 to 12 TB capacity ▪ A few drives with many tapes ▪ Juke boxes with petabytes (1000’s of TB) of storage