cloud: update node_storage_used_bytes metric description

tidb-cloud/monitor-datadog-integration.md

@@ -104,7 +104,7 @@ Datadog tracks the following metrics for your TiDB clusters.
 | tidb_cloud.db_command_per_second| gauge | type: Query\|StmtPrepare\|...<br/>cluster_name: `<cluster name>`<br/>instance: tidb-0\|tidb-1…<br/>component: `tidb` | The number of commands processed by TiDB per second, which is classified according to the success or failure of command execution results. |
 | tidb_cloud.db_queries_using_plan_cache_ops| gauge | cluster_name: `<cluster name>`<br/>instance: tidb-0\|tidb-1…<br/>component: `tidb` | The statistics of queries using [Plan Cache](/sql-prepared-plan-cache.md) per second. The execution plan cache only supports the prepared statement command. |
 | tidb_cloud.db_transaction_per_second| gauge | txn_mode: pessimistic\|optimistic<br/>type: abort\|commit\|...<br/>cluster_name: `<cluster name>`<br/>instance: tidb-0\|tidb-1…<br/>component: `tidb` | The number of transactions executed per second. |
-| tidb_cloud.node_storage_used_bytes | gauge | cluster_name: `<cluster name>`<br/>instance: tikv-0\|tikv-1…\|tiflash-0\|tiflash-1…<br/>component: tikv\|tiflash | The disk usage of TiKV/TiFlash nodes, in bytes. |
+| tidb_cloud.node_storage_used_bytes | gauge | cluster_name: `<cluster name>`<br/>instance: tikv-0\|tikv-1…\|tiflash-0\|tiflash-1…<br/>component: tikv\|tiflash | The disk usage, in bytes, for TiKV or TiFlash nodes. This metric primarily represents the logical data size in the storage engine, and excludes filesystem overhead, WAL files, and temporary files. To calculate the actual disk usage rate, use `(capacity - available) / capacity` instead. |
 | tidb_cloud.node_storage_capacity_bytes | gauge | cluster_name: `<cluster name>`<br/>instance: tikv-0\|tikv-1…\|tiflash-0\|tiflash-1…<br/>component: tikv\|tiflash | The disk capacity of TiKV/TiFlash nodes, in bytes. |
 | tidb_cloud.node_cpu_seconds_total | count | cluster_name: `<cluster name>`<br/>instance: tidb-0\|tidb-1…\|tikv-0…\|tiflash-0…<br/>component: tidb\|tikv\|tiflash | The CPU usage of TiDB/TiKV/TiFlash nodes. |
 | tidb_cloud.node_cpu_capacity_cores | gauge | cluster_name: `<cluster name>`<br/>instance: tidb-0\|tidb-1…\|tikv-0…\|tiflash-0…<br/>component: tidb\|tikv\|tiflash | The limit on CPU cores of TiDB/TiKV/TiFlash nodes. |

tidb-cloud/monitor-new-relic-integration.md

@@ -144,7 +144,7 @@ New Relic tracks the following metrics for your TiDB clusters.
 | tidb_cloud.db_command_per_second| gauge | type: Query\|StmtPrepare\|...<br/><br/>cluster_name: `<cluster name>`<br/><br/>instance: tidb-0\|tidb-1…<br/><br/>component: `tidb` | The number of commands processed by TiDB per second, which is classified according to the success or failure of command execution results. |
 | tidb_cloud.db_queries_using_plan_cache_ops| gauge | cluster_name: `<cluster name>`<br/><br/>instance: tidb-0\|tidb-1…<br/><br/>component: `tidb` | The statistics of queries using [Plan Cache](/sql-prepared-plan-cache.md) per second. The execution plan cache only supports the prepared statement command. |
 | tidb_cloud.db_transaction_per_second| gauge | txn_mode: pessimistic\|optimistic<br/><br/>type: abort\|commit\|...<br/><br/>cluster_name: `<cluster name>`<br/><br/>instance: tidb-0\|tidb-1…<br/><br/>component: `tidb` | The number of transactions executed per second. |
-| tidb_cloud.node_storage_used_bytes | gauge | cluster_name: `<cluster name>`<br/><br/>instance: tikv-0\|tikv-1…\|tiflash-0\|tiflash-1…<br/><br/>component: tikv\|tiflash | The disk usage of TiKV/TiFlash nodes, in bytes. |
+| tidb_cloud.node_storage_used_bytes | gauge | cluster_name: `<cluster name>`<br/><br/>instance: tikv-0\|tikv-1…\|tiflash-0\|tiflash-1…<br/><br/>component: tikv\|tiflash | The disk usage, in bytes, for TiKV or TiFlash nodes. This metric primarily represents the logical data size in the storage engine, and excludes filesystem overhead, WAL files, and temporary files. To calculate the actual disk usage rate, use `(capacity - available) / capacity` instead. |
 | tidb_cloud.node_storage_capacity_bytes | gauge | cluster_name: `<cluster name>`<br/><br/>instance: tikv-0\|tikv-1…\|tiflash-0\|tiflash-1…<br/><br/>component: tikv\|tiflash | The disk capacity of TiKV/TiFlash nodes, in bytes. |
 | tidb_cloud.node_cpu_seconds_total (Beta only) | count | cluster_name: `<cluster name>`<br/><br/>instance: tidb-0\|tidb-1…\|tikv-0…\|tiflash-0…<br/><br/>component: tidb\|tikv\|tiflash | The CPU usage of TiDB/TiKV/TiFlash nodes. |
 | tidb_cloud.node_cpu_capacity_cores | gauge | cluster_name: `<cluster name>`<br/><br/>instance: tidb-0\|tidb-1…\|tikv-0…\|tiflash-0…<br/><br/>component: tidb\|tikv\|tiflash | The limit on CPU cores of TiDB/TiKV/TiFlash nodes. |

tidb-cloud/monitor-prometheus-and-grafana-integration.md

@@ -116,7 +116,7 @@ Prometheus tracks the following metric data for your TiDB clusters.
 | tidbcloud_changefeed_latency | gauge | changefeed_id | The data replication latency between the upstream and the downstream of a changefeed |
 | tidbcloud_changefeed_checkpoint_ts | gauge | changefeed_id | The checkpoint timestamp of a changefeed, representing the largest TSO (Timestamp Oracle) successfully written to the downstream |
 | tidbcloud_changefeed_replica_rows | gauge | changefeed_id | The number of replicated rows that a changefeed writes to the downstream per second |
-| tidbcloud_node_storage_used_bytes | gauge | cluster_name: `<cluster name>`<br/>instance: `tikv-0\|tikv-1…\|tiflash-0\|tiflash-1…`<br/>component: `tikv\|tiflash` | The disk usage bytes of TiKV/TiFlash nodes |
+| tidbcloud_node_storage_used_bytes | gauge | cluster_name: `<cluster name>`<br/>instance: `tikv-0\|tikv-1…\|tiflash-0\|tiflash-1…`<br/>component: `tikv\|tiflash` | The disk usage, in bytes, for TiKV or TiFlash nodes. This metric primarily represents the logical data size in the storage engine, and excludes filesystem overhead, WAL files, and temporary files. To calculate the actual disk usage rate, use `(capacity - available) / capacity` instead. |
 | tidbcloud_node_storage_capacity_bytes | gauge | cluster_name: `<cluster name>`<br/>instance: `tikv-0\|tikv-1…\|tiflash-0\|tiflash-1…`<br/>component: `tikv\|tiflash` | The disk capacity bytes of TiKV/TiFlash nodes |
 | tidbcloud_node_cpu_seconds_total | count | cluster_name: `<cluster name>`<br/>instance: `tidb-0\|tidb-1…\|tikv-0…\|tiflash-0…`<br/>component: `tidb\|tikv\|tiflash` | The CPU usage of TiDB/TiKV/TiFlash nodes |
 | tidbcloud_node_cpu_capacity_cores | gauge | cluster_name: `<cluster name>`<br/>instance: `tidb-0\|tidb-1…\|tikv-0…\|tiflash-0…`<br/>component: `tidb\|tikv\|tiflash` | The CPU limit cores of TiDB/TiKV/TiFlash nodes |