Perchè nei settaggi è stato preferito lo scheduler cfq
CFQ
Completely Fair Queuing scheduler maintains a scalable per-process I/O queue and attempts to distribute the available I/O bandwidth equally among all I/O requests. Each per-process queue contains synchronous requests from processes. Time slice allocated for each queue depends on the priority of the 'parent' process. V2 of CFQ has some fixes which solves process' i/o starvation and some small backward seeks in the hope of improving responsiveness.
Advantages:
- Considered to deliver a balanced i/o performance.
- Easiest to tune.
- Excels on multiprocessor systems.
- Best database system performance after deadline.
Disadvantages:
- Some users report media scanning takes longest to complete using CFQ. This could be because of the property that since the bandwidth is equally distributed to all i/o operations during boot-up, media scanning is not given any special priority.
- Jitter (worst-case-delay) exhibited can sometimes be high, because of the number of tasks competing for the disk.