Update docs on asymmetric network partitions (#18953)

* Update docs on asymmetric network partitions

Fixes DOC-11224

Summary of changes:

- Provide more context on asymmetric partitions and how they're no
  longer a thing in CockroachDB v23.1+.  (Since that's quite an old
  version, we don't bother mentioning the version numbers.)

src/current/_includes/common/network-partitions.md

@@ -0,0 +1,7 @@
+A network partition occurs when two or more nodes are prevented from communicating with each other in one or both directions. A network partition can be caused by a network outage or a configuration problem with the network, such as when allowlisted IP addresses or hostnames change after a node is [drained and restarted]({% link {{ page.version.version }}/node-shutdown.md %}).
+
+In a **symmetric** partition, node communication is disrupted in both directions. In an **asymmetric** partition, nodes can communicate in one direction but not the other.
+
+CockroachDB protects against asymmetric partitions by converting all asymmetric (uni-directional) network partitions into symmetric (bi-directional) network partitions. This increases cluster resiliency by reducing the number of partition-related failures that can occur. Many temporary symmetric partitions can be recovered from automatically without operator intervention.
+
+The effect of a network partition depends on which nodes are partitioned, where the ranges are located, and to a large extent, whether [localities]({% link {{ page.version.version }}/cockroach-start.md %}#locality) or [zone configurations]({% link {{ page.version.version }}/configure-replication-zones.md %}) are defined. A partition that cuts off at least `(n-1)/2` replicas from a [range]({% link {{ page.version.version }}/architecture/overview.md %}#architecture-range) will cause range unavailability which will cause some data unavailability. If there are no localities or other constraints on where replicas are placed, then a partition of any ([`num_replicas`]({% link {{ page.version.version }}/configure-replication-zones.md %}#num_replicas) / 2) nodes will likely cause unavailability.

src/current/v23.1/cluster-setup-troubleshooting.md

@@ -232,9 +232,9 @@ Again, firewalls or hostname issues can cause any of these steps to fail.
 
 If the DB Console lists any dead nodes on the [**Cluster Overview** page]({% link {{ page.version.version }}/ui-cluster-overview-page.md %}), then you might have a network partition.
 
-**Explanation:** A network partition prevents nodes from communicating with each other in one or both directions. This can be due to a configuration problem with the network, such as when allowlisted IP addresses or hostnames change after a node is torn down and rebuilt. In a symmetric partition, node communication is broken in both directions. In an asymmetric partition, node communication works in one direction but not the other.
+**Explanation:** 
 
-The effect of a network partition depends on which nodes are partitioned, where the ranges are located, and to a large extent, whether [localities]({% link {{ page.version.version }}/cockroach-start.md %}#locality) are defined. If localities are not defined, a partition that cuts off at least (n-1)/2 nodes will cause data unavailability.
+{% include common/network-partitions.md %}
 
 **Solution:**
 

src/current/v23.1/ui-network-latency-page.md

@@ -35,11 +35,7 @@ For instance, the cluster shown above has nodes in `us-west1`, `us-east1`, and `
 
 Nodes that have lost a connection are displayed in a separate color. This can help you locate a network partition in your cluster.
 
-{{site.data.alerts.callout_info}}
-A network partition prevents nodes from communicating with each other in one or both directions. This can be due to a configuration problem with the network, such as when allowlisted IP addresses or hostnames change after a node is torn down and rebuilt. In a symmetric partition, node communication is broken in both directions. In an asymmetric partition, node communication works in one direction but not the other.
-
-The effect of a network partition depends on which nodes are partitioned, where the ranges are located, and to a large extent, whether [localities]({% link {{ page.version.version }}/cockroach-start.md %}#locality) are defined. If localities are not defined, a partition that cuts off at least (n-1)/2 nodes will cause data unavailability.
-{{site.data.alerts.end}}
+{% include common/network-partitions.md %}
 
 Click the **NO CONNECTIONS** link to see lost connections between nodes or [localities]({% link {{ page.version.version }}/cockroach-start.md %}#locality), if any are defined.
 

src/current/v23.2/cluster-setup-troubleshooting.md

@@ -232,9 +232,9 @@ If the DB Console
 
 then you might have a network partition.
 
-**Explanation:** A network partition occurs when two or more nodes are prevented from communicating with each other in one or both directions. A network partition can be caused by a network outage or a configuration problem with the network, such as when allowlisted IP addresses or hostnames change after a node is torn down and rebuilt. In a symmetric partition, node communication is disrupted in both directions. In an asymmetric partition, nodes can communicate in one direction but not the other.
+**Explanation:**
 
-The effect of a network partition depends on which nodes are partitioned, where the ranges are located, and to a large extent, whether [localities]({% link {{ page.version.version }}/cockroach-start.md %}#locality) are defined. If localities are not defined, a partition that cuts off at least (n-1)/2 nodes will cause data unavailability.
+{% include common/network-partitions.md %}
 
 **Solution:**
 

src/current/v23.2/ui-network-latency-page.md

@@ -57,9 +57,7 @@ Hover over a cell to display more details:
 This specific information can help you understand the root cause of the connectivity issue.
 
 {{site.data.alerts.callout_info}}
-A network partition occurs when two or more nodes are prevented from communicating with each other in one or both directions. A network partition can be caused by a network outage or a configuration problem with the network, such as when allowlisted IP addresses or hostnames change after a node is torn down and rebuilt. In a symmetric partition, node communication is disrupted in both directions. In an asymmetric partition, nodes can communicate in one direction but not the other.
-
-The effect of a network partition depends on which nodes are partitioned, where the ranges are located, and to a large extent, whether [localities]({% link {{ page.version.version }}/cockroach-start.md %}#locality) are defined. If localities are not defined, a partition that cuts off at least (n-1)/2 nodes will cause data unavailability.
+{% include common/network-partitions.md %}
 {{site.data.alerts.end}}
 
 ### Node liveness status

src/current/v24.1/cluster-setup-troubleshooting.md

@@ -232,9 +232,9 @@ If the DB Console
 
 then you might have a network partition.
 
-**Explanation:** A network partition occurs when two or more nodes are prevented from communicating with each other in one or both directions. A network partition can be caused by a network outage or a configuration problem with the network, such as when allowlisted IP addresses or hostnames change after a node is torn down and rebuilt. In a symmetric partition, node communication is disrupted in both directions. In an asymmetric partition, nodes can communicate in one direction but not the other.
+**Explanation:**
 
-The effect of a network partition depends on which nodes are partitioned, where the ranges are located, and to a large extent, whether [localities]({% link {{ page.version.version }}/cockroach-start.md %}#locality) are defined. If localities are not defined, a partition that cuts off at least (n-1)/2 nodes will cause data unavailability.
+{% include common/network-partitions.md %}
 
 **Solution:**
 

src/current/v24.1/ui-network-latency-page.md

@@ -57,9 +57,7 @@ Hover over a cell to display more details:
 This specific information can help you understand the root cause of the connectivity issue.
 
 {{site.data.alerts.callout_info}}
-A network partition occurs when two or more nodes are prevented from communicating with each other in one or both directions. A network partition can be caused by a network outage or a configuration problem with the network, such as when allowlisted IP addresses or hostnames change after a node is torn down and rebuilt. In a symmetric partition, node communication is disrupted in both directions. In an asymmetric partition, nodes can communicate in one direction but not the other.
-
-The effect of a network partition depends on which nodes are partitioned, where the ranges are located, and to a large extent, whether [localities]({% link {{ page.version.version }}/cockroach-start.md %}#locality) are defined. If localities are not defined, a partition that cuts off at least (n-1)/2 nodes will cause data unavailability.
+{% include common/network-partitions.md %}
 {{site.data.alerts.end}}
 
 ### Node liveness status

src/current/v24.2/cluster-setup-troubleshooting.md

@@ -232,9 +232,9 @@ If the DB Console
 
 then you might have a network partition.
 
-**Explanation:** A network partition occurs when two or more nodes are prevented from communicating with each other in one or both directions. A network partition can be caused by a network outage or a configuration problem with the network, such as when allowlisted IP addresses or hostnames change after a node is torn down and rebuilt. In a symmetric partition, node communication is disrupted in both directions. In an asymmetric partition, nodes can communicate in one direction but not the other.
+**Explanation:**
 
-The effect of a network partition depends on which nodes are partitioned, where the ranges are located, and to a large extent, whether [localities]({% link {{ page.version.version }}/cockroach-start.md %}#locality) are defined. If localities are not defined, a partition that cuts off at least (n-1)/2 nodes will cause data unavailability.
+{% include common/network-partitions.md %}
 
 **Solution:**
 

src/current/v24.2/ui-network-latency-page.md

@@ -57,9 +57,7 @@ Hover over a cell to display more details:
 This specific information can help you understand the root cause of the connectivity issue.
 
 {{site.data.alerts.callout_info}}
-A network partition occurs when two or more nodes are prevented from communicating with each other in one or both directions. A network partition can be caused by a network outage or a configuration problem with the network, such as when allowlisted IP addresses or hostnames change after a node is torn down and rebuilt. In a symmetric partition, node communication is disrupted in both directions. In an asymmetric partition, nodes can communicate in one direction but not the other.
-
-The effect of a network partition depends on which nodes are partitioned, where the ranges are located, and to a large extent, whether [localities]({% link {{ page.version.version }}/cockroach-start.md %}#locality) are defined. If localities are not defined, a partition that cuts off at least (n-1)/2 nodes will cause data unavailability.
+{% include common/network-partitions.md %}
 {{site.data.alerts.end}}
 
 ### Node liveness status

src/current/v24.3/cluster-setup-troubleshooting.md

@@ -232,9 +232,9 @@ If the DB Console
 
 then you might have a network partition.
 
-**Explanation:** A network partition occurs when two or more nodes are prevented from communicating with each other in one or both directions. A network partition can be caused by a network outage or a configuration problem with the network, such as when allowlisted IP addresses or hostnames change after a node is torn down and rebuilt. In a symmetric partition, node communication is disrupted in both directions. In an asymmetric partition, nodes can communicate in one direction but not the other.
+**Explanation:**
 
-The effect of a network partition depends on which nodes are partitioned, where the ranges are located, and to a large extent, whether [localities]({% link {{ page.version.version }}/cockroach-start.md %}#locality) are defined. If localities are not defined, a partition that cuts off at least (n-1)/2 nodes will cause data unavailability.
+{% include common/network-partitions.md %}
 
 **Solution:**
 

src/current/v24.3/ui-network-latency-page.md

@@ -57,9 +57,7 @@ Hover over a cell to display more details:
 This specific information can help you understand the root cause of the connectivity issue.
 
 {{site.data.alerts.callout_info}}
-A network partition occurs when two or more nodes are prevented from communicating with each other in one or both directions. A network partition can be caused by a network outage or a configuration problem with the network, such as when allowlisted IP addresses or hostnames change after a node is torn down and rebuilt. In a symmetric partition, node communication is disrupted in both directions. In an asymmetric partition, nodes can communicate in one direction but not the other.
-
-The effect of a network partition depends on which nodes are partitioned, where the ranges are located, and to a large extent, whether [localities]({% link {{ page.version.version }}/cockroach-start.md %}#locality) are defined. If localities are not defined, a partition that cuts off at least (n-1)/2 nodes will cause data unavailability.
+{% include common/network-partitions.md %}
 {{site.data.alerts.end}}
 
 ### Node liveness status