29.12.22.9 The system_disk_stats Table

I/O statistics of available block devices.

mysql> select * from performance_schema.system_disk_stats\G
*************************** 1. row ***************************
    TIMESTAMP: 2026-09-30 17:00:05
       DEVICE: dm-0
   READ_COUNT: 42907
   READ_BYTES: 2680155136
 READ_TIME_MS: 46800
  WRITE_COUNT: 15929
  WRITE_BYTES: 853848064
WRITE_TIME_MS: 43456
      FLUSHES: 0
FLUSH_TIME_MS: 0
*************************** 2. row ***************************
    TIMESTAMP: 2026-09-30 17:00:05
       DEVICE: dm-1
   READ_COUNT: 98
   READ_BYTES: 2273280
 READ_TIME_MS: 82
  WRITE_COUNT: 482
  WRITE_BYTES: 1974272
WRITE_TIME_MS: 898
      FLUSHES: 0
FLUSH_TIME_MS: 0
*************************** 3. row ***************************
    TIMESTAMP: 2026-09-30 17:00:05
       DEVICE: dm-2
   READ_COUNT: 37008
   READ_BYTES: 967839744
 READ_TIME_MS: 32443
  WRITE_COUNT: 16983
  WRITE_BYTES: 287459328
WRITE_TIME_MS: 33627
      FLUSHES: 0
FLUSH_TIME_MS: 0
*************************** 4. row ***************************

The system_disk_stats table has the following columns:

• TIMESTAMP: Time when the measurement was taken.

• DEVICE: Device name.

• READ_COUNT: Reads completed successfully

• READ_BYTES: Number of bytes read

• READ_TIME_MS: Time spent reading, in milliseconds

• WRITE_COUNT: Writes completed successfully

• WRITE_BYTES: Number of bytes written

• WRITE_TIME_MS: Time spent writing, in milliseconds

• FLUSHES: Flush requests completed successfully

• FLUSH_TIME_MS: Time spent flushing, in milliseconds