To display block I/O metrics (input/output) on a PostgreSQL server, you can use various methods and tools. Here are some options:

1. pg_stat_statements:
   • PostgreSQL’s pg_stat_statements extension can provide insight into the number of blocks read and written by specific queries. To use it, you need to enable the extension and monitor the pg_stat_statements view.
   First, enable the extension by adding or uncommenting the following line in your postgresql.conf file and then restarting PostgreSQL:shared_preload_libraries = 'pg_stat_statements' After that, you can query the pg_stat_statements view to see I/O statistics for specific queries:SELECT query, total_time, rows, shared_blks_read, shared_blks_hit, local_blks_read, local_blks_hit, temp_blks_read, temp_blks_written FROM pg_stat_statements; This query will display I/O metrics for the recorded statements.
2. pg_stat_activity:
   • You can also use the pg_stat_activity view to monitor ongoing queries and check their I/O activity. This view includes information about the current query being executed, such as the number of blocks read and written.SELECT pid, query, pg_size_pretty(pg_stat_get_blocks_fetched(pid)) AS blocks_fetched, pg_size_pretty(pg_stat_get_blocks_hit(pid)) AS blocks_hit FROM pg_stat_activity; This query shows the process ID (pid), the query being executed (query), the number of blocks fetched, and the number of blocks hit in the shared buffer cache.
3. pg_stat_bgwriter:
   • The pg_stat_bgwriter view provides statistics about the background writer process, which manages PostgreSQL’s background I/O operations. It includes information about buffers written and other I/O-related metrics.SELECT checkpoints_timed, buffers_heckpoint, buffers_clean, buffers_backend, buffers_alloc FROM pg_stat_bgwriter; This query will show various I/O-related metrics related to background writing.
4. Operating System Tools:
   • You can also use operating system-level monitoring tools to track I/O metrics for the PostgreSQL process. Common tools include iostat on Linux and Task Manager on Windows. These tools can provide system-wide I/O metrics, including disk reads and writes by the PostgreSQL process.
   For example, on Linux, you can run the following command to monitor disk I/O for the PostgreSQL process: iostat -xk 1 | grep postgres This command will display real-time I/O metrics for the PostgreSQL process.

Remember that monitoring I/O metrics can help identify performance bottlenecks and optimize your PostgreSQL database for better performance. Consider using a combination of these methods to gain a comprehensive understanding of your system’s I/O activity.