5.2 Database File I/O pages

The Database File I/O By Host dashboard summarizes the file I/O, grouped by host.

Table 5.2 Database File I/O By Host

Name	Description
Host	The host from which the client connected. Rows for which the HOST column in the underlying Performance Schema table is NULL are assumed to be for background threads and are reported with a host name of `background`.
Total	The total number of file I/O events for the host.
Total Latency	The total wait time of timed file I/O events for the host.

The Database File I/O By Thread dashboard summarizes I/O consumers to display time waiting for I/O, grouped by thread.

Table 5.3 Database File I/O By Thread

Name	Description
Thread ID	The thread identifier.
User	For foreground threads, the account associated with the thread. For background threads, the thread name.
Average Latency	The average wait time per timed I/O event for the thread.
Max Latency	The maximum single wait time of timed I/O events for the thread.
Min Latency	The minimum single wait time of timed I/O events for the thread.
Process List ID	For foreground threads, the processlist ID of the thread. For background threads, NULL.
Total	The total number of I/O events for the thread.
Total Latency	The total wait time of timed I/O events for the thread.

The Database File I/O By File dashboard summarizes global I/O consumers to display amount of I/O, grouped by file.

Table 5.4 Database File I/O By File

Name	Description
File	The file path name.
Count Misc	The total number of other I/O events for the file.
Count Read	The total number of read I/O events for the file.
Count Write	The total number of write I/O events for the file.
Misc Latency	The total wait time of timed other I/O events for the file.
Total	The total number of I/O events for the file.
Total Latency	The total wait time of timed I/O events for the file.
Write Latency	The total wait time of timed write I/O events for the file.

The Database File I/O By Type dashboard summarizes global I/O consumers to display amount of I/O and time waiting for I/O, grouped by event.

Table 5.5 Database File I/O By Type

Name	Description
Event	The I/O event name, with the wait/io/file/ prefix stripped.
Average Latency	The average wait time per timed occurrence of the I/O event.
Average Read	The average number of bytes per read for the I/O event.
Average Written	The average number of bytes per write for the I/O event.
Count Read	The number of read requests for the I/O event.
Count Write	The number of write requests for the I/O event.
Max Latency	The maximum single wait time of timed occurrences of the I/O event.
Misc Latency	The total wait time of timed other occurrences of the I/O event.
Read Latency	The total wait time of timed read occurrences of the I/O event.
Total	The total number of occurrences of the I/O event.
Total Latency	The total wait time of timed occurrences of the I/O event.
Total Read	The number of bytes read for the I/O event.
Total Written	The number of bytes written for the I/O event.
Write Latency	The total wait time of timed write occurrences of the I/O event.

The InnoDB File I/O dashboard displays information on the various file I/O activity on the monitored server.

Table 5.6 InnoDB File I/O Performance Page Regions

Name	Description
Data File IO Activity (bytes)	Graphs the amount of data read and written, in bytes.
Data File IO Activity (ops)	Graphs the number of fsync() operations, data reads and writes.
Average Bytes Per Read	Graphs the average bytes per read.
Double Write Activity	Graphs the number of doublewrite operations and the number of pages written for doublewrite operations.
Redo Log IO Activity (bytes)	Graphs the number of bytes written to the log file.
Redo Log IO Activity (ops)	Graphs the number of log write requests and the number of physical log writes.
Redo Log Waits	Graphs the number of times the log buffer was too small and had to be flushed.
Pending IO	Graphs the number of pending asynchronous I/O read/write requests,
Pending Flushes	Graphs the number of pending buffer and redo log flush operations.
Open Files	Graphs the number of open files in InnoDB.
InnoDB IO Configuration	Lists the InnoDB IO-specific system variables and their values.