Flash Storage NOR flash vs NAND flash ■NAND flash used widely for storage,cheaper than NOR flash requires page-at-a-time read(page:512 bytes to 4 KB) 20 to 100 microseconds for a page read Not much difference between sequential and random read Page can only be written once Must be erased to allow rewrite ■Solid state disks Use standard block-oriented disk interfaces,but store data on multiple flash storage devices internally Transfer rate of up to 500 MB/sec using SATA,and up to 3 GB/sec using NVMe PCle Database System Concepts-7th Edition 12.12 ©Silberscha乜，Korth and SudarshanDatabase System Concepts - 7 12.12 ©Silberschatz, Korth and Sudarshan th Edition Flash Storage ▪ NOR flash vs NAND flash ▪ NAND flash • used widely for storage, cheaper than NOR flash • requires page-at-a-time read (page: 512 bytes to 4 KB) ▪ 20 to 100 microseconds for a page read ▪ Not much difference between sequential and random read • Page can only be written once ▪ Must be erased to allow rewrite ▪ Solid state disks • Use standard block-oriented disk interfaces, but store data on multiple flash storage devices internally • Transfer rate of up to 500 MB/sec using SATA, and up to 3 GB/sec using NVMe PCIe