Scalability - Harvard lecture

https://www.youtube.com/watch?v=-W9F__D3oY4

Vertical Scaling

• CPU: cores, L2 cache

• Disk

• RAM

Horizontal Scaling

• multiple servers

• then we need to distribute requests - load balancer

load balancer

• round robin is not so good if there's some heavy users in specific server

• RAID (redundant array of independent disks) - RAID works by placing data on multiple disks and allowing input/output (I/O) operations to overlap in a balanced way, improving performance. Because the use of multiple disks increases the mean time between failures (MTBF), storing data redundantly also increases fault tolerance.

• Software: ELB, HAProxy

• Hardware

Sticky sessions - 断电之类的 single failure

• shared storage

• cookies

Caching

• .html

• MySQL Query Cache

• memcached

Replication

• Master-slave

• Master-master