01. I/O common query commands
View system disk I/O status (top, vmstat, iostat)
[root@ufo130 ~]# iostat -dx
- r/s and w/s are the number of read operations and write operations per second, respectively
- The rKB/s and wKB/s columns show the amount of data read and written in kilobytes per second
- If these two pairs of data values are both high, it means that disk io operations are very frequent
View process I/O status (iotop, pidstat)
02. Synchronous and asynchronous I/O
Synchronization : Until the dirty page is flushed to the disk, it returns success, and the whole process only does one thing, waits for death.
Asynchronous : Call the refresh function for the first time, wait for the return prompt, and you can do other things during the whole process without waiting.
Dirty page loss : Whether the entire process can tolerate data loss, etc. (special reference for the database), usually dirty pages will be automatically flushed to the disk under normal circumstances, including normal shutdown, or manually, (but when the power is down, and The server does not have internal battery power to refresh the dirty pages in time, and the data in the dirty pages will be lost).