In InnoDB, data files are managed using a combination of data dictionary tables and system tablespace files.
Data dictionary tables: InnoDB stores metadata about the database, such as table and index definitions, in data dictionary tables. These tables are stored in the InnoDB system tablespace, which is a shared tablespace that contains the InnoDB data dictionary and other system-level information.
System tablespace files: InnoDB stores all the data in tables and indexes, as well as undo logs, in system tablespace files. The system tablespace files are typically located in the MySQL data directory, and are named ibdata1, ibdata2, etc.
Additional tablespaces: InnoDB also supports creating additional tablespaces, which allows for separating different tables and indexes into different files. This can be useful for managing large tables, spreading I/O across multiple disks, or for backup and recovery purposes.
File-per-table: This is another feature of InnoDB which allows you to store the data and indexes of individual tables in separate files, rather than in the shared system tablespace. This can be useful for managing large tables, spreading I/O across multiple disks, or for backup and recovery purposes.
InnoDB uses a combination of data dictionary tables and system tablespace files to manage data files. The system tablespace files store all the data in tables and indexes, as well as undo logs, while the data dictionary tables store metadata about the database, such as table and index definitions. InnoDB also supports creating additional tablespaces and file-per-table feature which allows to separate different tables and indexes into different files.
Here is an example of a Python script that uses the psutil library to monitor disk I/O in InnoDB in real-time:
This script uses the psutil.disk_io_counters() function to get the disk I/O statistics, which returns an object containing the number of bytes read and written. The script then prints these values to the console.
It uses a while loop to continuously monitor the disk I/O statistics with a specified interval using the time.sleep(interval) function. The interval variable can be set to any value in seconds. The script will print the disk I/O statistics every interval seconds.
You can also modify the script to save the data to a file or database, or to send an alert if the disk I/O exceeds a certain threshold.
It's important to note that this script only monitors disk I/O at the system level, it does not provide specific metrics for InnoDB. To get specific metrics for InnoDB, you would need to query the performance_schema tables in MySQL or use some other monitoring tool that can collect and present InnoDB specific metrics.
Open Source Database Systems Engineer with a deep understanding of Optimizer Internals, Performance Engineering, Scalability and Data SRE. Shiv currently is the Founder, Investor, Board Member and CEO of multiple Database Systems Infrastructure Operations companies in the Transaction Processing Computing and ColumnStores ecosystem. He is also a frequent speaker in open source software conferences globally.