Lecture 1 Overview and Flash SSD Operation

Storage Systems

Memory/storage hierarchy
- Balancing performance with cost
  - Small memories are fast but expensive
  - Large memories are slow but cheap
- Exploit locality to get the best of both worlds
  - locality = re-use/nearness of accesses
  - allows most accesses to use small, fast memory
- Locality is a general concept
  - power, BW, management
Persistence
- Storing data for lengthy periods of time
  - despite component failures, SW bugs/upgrades, human error
- To be useful, it must also be possible to find it again later
  - this brings in data organization, consistency, and management issues
- This is where the serious action is
  - and it does relate to the memory/storage hierarchy

Software and Hardware that collectively provide application writers with an infrastructure that retains persistent data and provides it on request
Logical: Program <--> File System <- -> Controller Firmware
Physical: Client <--> Server <--> I/O Controller <--> Device ASIC
Storage Software Interfaces
- Program <--> Physical Media
- Naming and address mapping (e.g., relocation)
- Caching and request transformations (e.g., combining)