Move TiFlash troubleshoot part to a new document

TOC.md

@@ -334,6 +334,7 @@
     - [Configure TiFlash](/tiflash/tiflash-configuration.md)
     - [TiFlash Alert Rules](/tiflash/tiflash-alert-rules.md)
     - [Tune TiFlash Performance](/tiflash/tune-tiflash-performance.md)
+    - [Troubleshoot a TiFlash Cluster](/tiflash/troubleshoot-tiflash.md)
     - [FAQ](/tiflash/tiflash-faq.md)
   + TiDB Binlog
     - [Overview](/tidb-binlog/tidb-binlog-overview.md)

tiflash/maintain-tiflash.md

@@ -7,7 +7,7 @@ aliases: ['/docs/dev/reference/tiflash/maintain/']
 
 # Maintain a TiFlash Cluster
 
-This document describes how to perform common operations when you maintain a TiFlash cluster, including checking the TiFlash version, taking TiFlash nodes down, and troubleshooting TiFlash. This document also introduces critical logs and a system table of TiFlash.
+This document describes how to perform common operations when you maintain a TiFlash cluster, including checking the TiFlash version, and taking TiFlash nodes down. This document also introduces critical logs and a system table of TiFlash.
 
 ## Check the TiFlash version
 
@@ -102,70 +102,6 @@ To manually delete the replication rules in PD, take the following steps:
     curl -v -X DELETE http://<pd_ip>:<pd_port>/pd/api/v1/config/rule/tiflash/table-45-r
     ```
 
-## TiFlash troubleshooting
-
-This section describes some commonly encountered issues when using TiFlash, the reasons, and the solutions.
-
-### TiFlash replica is always unavailable
-
-This is because TiFlash is in an abnormal state caused by configuration errors or environment issues. Take the following steps to identify the faulty component:
-
-1. Check whether PD enables the `Placement Rules` feature (to enable the feature, see the step 2 of [Add TiFlash component to an existing TiDB cluster](/tiflash/deploy-tiflash.md#add-tiflash-component-to-an-existing-tidb-cluster):
-
-    {{< copyable "shell-regular" >}}
-
-    ```shell
-    echo 'config show replication' | /path/to/pd-ctl -u http://<pd-ip>:<pd-port>
-    ```
-
-    The expected result is `"enable-placement-rules": "true"`.
-
-2. Check whether the TiFlash process is working correctly by viewing `UpTime` on the TiFlash-Summary monitoring panel.
-
-3. Check whether the TiFlash proxy status is normal through `pd-ctl`.
-
-    {{< copyable "shell-regular" >}}
-
-    ```shell
-    echo "store" | /path/to/pd-ctl -u http://<pd-ip>:<pd-port>
-    ```
-
-    The TiFlash proxy's `store.labels` includes information such as `{"key": "engine", "value": "tiflash"}`. You can check this information to confirm a TiFlash proxy.
-
-4. Check whether `pd buddy` can correctly print the logs (the log path is the value of `log` in the [flash.flash_cluster] configuration item; the default log path is under the `tmp` directory configured in the TiFlash configuration file).
-
-5. Check whether the value of `max-replicas` in PD is less than or equal to the number of TiKV nodes in the cluster. If not, PD cannot replicate data to TiFlash:
-
-    {{< copyable "shell-regular" >}}
-
-    ```shell
-    echo 'config show replication' | /path/to/pd-ctl -u http://<pd-ip>:<pd-port>
-    ```
-
-    Reconfirm the value of `max-replicas`.
-
-6. Check whether the remaining disk space of the machine (where `store` of the TiFlash node is) is sufficient. By default, when the remaining disk space is less than 20% of the `store` capacity (which is controlled by the `low-space-ratio` parameter), PD cannot schedule data to this TiFlash node.
-
-### TiFlash query time is unstable, and the error log prints many `Lock Exception` messages
-
-This is because large amounts of data are written to the cluster, which causes that the TiFlash query encounters a lock and requires query retry.
-
-You can set the query timestamp to one second earlier in TiDB. For example, if the current time is '2020-04-08 20:15:01', you can execute `set @@tidb_snapshot='2020-04-08 20:15:00';` before you execute the query. This makes less TiFlash queries encounter a lock and mitigates the risk of unstable query time.
-
-### Some queries return the `Region Unavailable` error
-
-If the load pressure on TiFlash is too heavy and it causes that TiFlash data replication falls behind, some queries might return the `Region Unavailable` error.
-
-In this case, you can balance the load pressure by adding more TiFlash nodes.
-
-### Data file corruption
-
-Take the following steps to handle the data file corruption:
-
-1. Refer to [Take a TiFlash node down](#take-a-tiflash-node-down) to take the corresponding TiFlash node down.
-2. Delete the related data of the TiFlash node.
-3. Redeploy the TiFlash node in the cluster.
-
 ## TiFlash critical logs
 
 | Log Information | Log Description |

tiflash/troubleshoot-tiflash.md

@@ -0,0 +1,69 @@
+---
+title: Troubleshoot a TiFlash Cluster
+summary: Learn common operations when you troubleshoot a TiFlash cluster.
+category: reference
+---
+
+# Troubleshoot a TiFlash Cluster
+
+This section describes some commonly encountered issues when using TiFlash, the reasons, and the solutions.
+
+## TiFlash replica is always unavailable
+
+This is because TiFlash is in an abnormal state caused by configuration errors or environment issues. Take the following steps to identify the faulty component:
+
+1. Check whether PD enables the `Placement Rules` feature (to enable the feature, see the step 2 of [Add TiFlash component to an existing TiDB cluster](/tiflash/deploy-tiflash.md#add-tiflash-component-to-an-existing-tidb-cluster):
+
+    {{< copyable "shell-regular" >}}
+
+    ```shell
+    echo 'config show replication' | /path/to/pd-ctl -u http://<pd-ip>:<pd-port>
+    ```
+
+    The expected result is `"enable-placement-rules": "true"`.
+
+2. Check whether the TiFlash process is working correctly by viewing `UpTime` on the TiFlash-Summary monitoring panel.
+
+3. Check whether the TiFlash proxy status is normal through `pd-ctl`.
+
+    {{< copyable "shell-regular" >}}
+
+    ```shell
+    echo "store" | /path/to/pd-ctl -u http://<pd-ip>:<pd-port>
+    ```
+
+    The TiFlash proxy's `store.labels` includes information such as `{"key": "engine", "value": "tiflash"}`. You can check this information to confirm a TiFlash proxy.
+
+4. Check whether `pd buddy` can correctly print the logs (the log path is the value of `log` in the [flash.flash_cluster] configuration item; the default log path is under the `tmp` directory configured in the TiFlash configuration file).
+
+5. Check whether the value of `max-replicas` in PD is less than or equal to the number of TiKV nodes in the cluster. If not, PD cannot replicate data to TiFlash:
+
+    {{< copyable "shell-regular" >}}
+
+    ```shell
+    echo 'config show replication' | /path/to/pd-ctl -u http://<pd-ip>:<pd-port>
+    ```
+
+    Reconfirm the value of `max-replicas`.
+
+6. Check whether the remaining disk space of the machine (where `store` of the TiFlash node is) is sufficient. By default, when the remaining disk space is less than 20% of the `store` capacity (which is controlled by the `low-space-ratio` parameter), PD cannot schedule data to this TiFlash node.
+
+## TiFlash query time is unstable, and the error log prints many `Lock Exception` messages
+
+This is because large amounts of data are written to the cluster, which causes that the TiFlash query encounters a lock and requires query retry.
+
+You can set the query timestamp to one second earlier in TiDB. For example, if the current time is '2020-04-08 20:15:01', you can execute `set @@tidb_snapshot='2020-04-08 20:15:00';` before you execute the query. This makes less TiFlash queries encounter a lock and mitigates the risk of unstable query time.
+
+## Some queries return the `Region Unavailable` error
+
+If the load pressure on TiFlash is too heavy and it causes that TiFlash data replication falls behind, some queries might return the `Region Unavailable` error.
+
+In this case, you can balance the load pressure by adding more TiFlash nodes.
+
+## Data file corruption
+
+Take the following steps to handle the data file corruption:
+
+1. Refer to [Take a TiFlash node down](#take-a-tiflash-node-down) to take the corresponding TiFlash node down.
+2. Delete the related data of the TiFlash node.
+3. Redeploy the TiFlash node in the cluster.