IO

Persistent Disk Benchmarking

Benchmarking persistent disk performance

fio

Buffered I/O vs. Unbuffered I/O

https://stackoverflow.com/questions/1450551/buffered-vs-unbuffered-io

• Buffered I/O: program structures -> file buffer -> kernel buffer -> disk

  • minimizes system calls

  • minimizes disk I/O

• Unbuffered I/O: program structures -> kernel buffer -> disk

  • Used when we want output to be written before continuing (e.g. stderr under C runtime library is usually unbuffered by default, logging library)

Example:

• Program reads file 1 byte at a time

• Unbuffered input: goes to disk for every byte (slow)

• Buffered input: Whole block is read into buffer, then individual bytes delivered from buffer area (faster)