Write Optimized Indices Performance of B+-trees can be poor for write-intensive workloads One 1/O per leaf,assuming all internal nodes are in memory With magnetic disks,100 inserts per second per disk With flash memory,one page overwrite per insert Two approaches to reducing cost of writes Log-structured merge tree ·Buffer tree Database System Concepts-7th Edition 24.4 ©Silberscha乜，Korth and SudarshanDatabase System Concepts - 7 24.4 ©Silberschatz, Korth and Sudarshan th Edition Write Optimized Indices ▪ Performance of ▪ B + -trees can be poor for write-intensive workloads • One I/O per leaf, assuming all internal nodes are in memory • With magnetic disks, < 100 inserts per second per disk • With flash memory, one page overwrite per insert ▪ Two approaches to reducing cost of writes • Log-structured merge tree • Buffer tree