PCSM 286 289 cross version replication

_resource/overrides/main.html

@@ -6,6 +6,32 @@
 {# Import the theme's layout. #}
 {% extends "base.html" %}
 
+{% block announce %}
+  <div class="md-banner" style="text-align: center;">
+    Where the open source database community meets:
+    Use code <strong>PERCONA75</strong> and secure your spot for Percona Live.
+
+    <a
+      class="breakdance-link button-atom button-atom--primary bde-button__button"
+      href="https://perconalive.com/2026-usa/"
+      target="_blank"
+      data-type="url"
+      style="
+        padding: 5px 20px;
+        display: inline-block;
+        margin-left: 10px;
+        background-color: #1fa23a;
+        border-radius: 999px;
+        text-decoration: none;
+      "
+    >
+      <span class="button-atom__text" style="font-size: 16px; color: #ffffff;">
+        Register
+      </span>
+    </a>
+  </div>
+{% endblock %}
+
 {% block scripts %}
 <script src="https://cmp.osano.com/Azqe5vTyLOSbN3OuT/49ad85b5-0418-4794-ab81-7599dddd534c/osano.js"></script>
 {{ super() }}

docs/css/extra.css

@@ -59,3 +59,14 @@
   font-size: 0.6rem !important;         /* smaller font */
   color: var(--md-typeset-a-color);
 }
+
+/* Percona live announcement banner */
+
+.md-banner {
+  text-align: center;
+}
+
+.md-banner,
+.md-banner * {
+  font-family: "Poppins", sans-serif !important;
+}

docs/limitations.md

@@ -41,7 +41,6 @@ The following functionalities are not supported:
 
 * Multiple source or multiple target clusters 
 * You cannot resume initial synchronization if an issue occurred. You must start it from scratch.
-* Database upgrade during the sync, even in the paused state.
+* Arbitrary database upgrades during a sync are not supported. For supported staged upgrades from lower to higher MongoDB major versions, follow the cross-version replication procedure.
 * Reverse synchronization
 * External authentication via Kerberos, AWS and LDAP
-* [GridFS :octicons-link-external-16:](https://www.mongodb.com/docs/manual/core/gridfs/)

docs/release-notes.md

@@ -4,6 +4,8 @@
 
     Starting with version 0.7.0, Percona Link for MongoDB has been rebranded as Percona ClusterSync for MongoDB. Any mentions of Percona Link for MongoDB in earlier release notes now refer to this product.
 
+* Percona ClusterSync for MongoDB 0.8.1 ({{date.v0_8_1}})
+
 * [Percona ClusterSync for MongoDB 0.8.0 ({{date.v0_8_0}})](release-notes/0.8.0.md)
 
 * [Percona ClusterSync for MongoDB 0.7.0 ({{date.v0_7_0}})](release-notes/0.7.0.md)

docs/version-compatibility.md

@@ -0,0 +1,50 @@
+# Cross-version replication
+
+{{pcsm.full_name}} (PCSM) supports replication only for the MongoDB major-version combinations listed in the compatibility matrix below. In the current release, this includes clusters running the same major version and selected lower-to-higher upgrade paths. This lets you synchronize data during a staged upgrade or maintain replication across clusters that run different versions where support is explicitly provided.
+
+At startup, PCSM checks whether the source and target major-version combination is listed as supported in the compatibility matrix below. If the combination is not supported, PCSM blocks startup and exits with an error, including all cases where the source major version is higher than the target major version.
+
+## Supported scenarios
+
+PCSM supports synchronization only for version combinations explicitly marked as supported in the compatibility matrix below.
+
+In the current release, supported scenarios are:
+
+- Both clusters run the same major version.
+- The target cluster runs the next supported higher major version shown in the matrix.
+
+PCSM blocks synchronization in all cases where the source major version is higher than the target major version. Combinations that are not listed as supported in the matrix are not supported in the current release.
+
+## Version compatibility matrix
+
+| Source version | Target version | Supported | Notes |
+|----------------|----------------|-----------|-------|
+| 6.0.x | 6.0.x | **Yes** | — |
+| 6.0.x | 7.0.x | **Yes** | — |
+| 6.0.x | 8.0.x | **Yes** | — |
+| 7.0.x | 7.0.x | **Yes** | — |
+| 7.0.x | 8.0.x | **Yes** | — |
+| 8.0.x | 7.0.x | **No** | Downgrade replication is not supported. |
+| 7.0.x | 6.0.x | **No** | Downgrade replication is not supported. |
+| Any higher | Any lower | **No** | Downgrade paths are not supported. |
+
+Use only the version combinations listed as supported in the table above. Unsupported combinations may start successfully but are not tested or officially supported.
+
+## Limitations
+
+- **Feature Compatibility Version (FCV) is not automatically checked between your source and target clusters**
+
+    PCSM does not automatically check the Feature Compatibility Version (FCV) between your source and target clusters. Because an incompatible FCV might cause replication failures, it is important to perform this check manually before you begin:
+
+    Confirm the FCV for both your source and target clusters.
+    Ensure the target cluster's FCV is equal to or higher than the source cluster's FCV.
+
+- **Downgrade replication is not supported**
+
+    PCSM blocks startup if the source major version is higher than the target major version.
+
+
+- **Version compatibility is checked only at startup** 
+
+    PCSM performs the version check once when the server starts. This check is not repeated when replication is started or resumed.
+

mkdocs-base.yml

@@ -168,6 +168,7 @@ nav:
   - Get started:
       - Quickstart: installation.md
       - System requirements: system-requirements.md
+      - Cross-version replication: version-compatibility.md
       - 1. Install:
         - From repositories: install/repos.md
         - Run in Docker: install/docker.md

variables.yml

@@ -2,10 +2,10 @@
 # See also mkdocs.yml plugins.with-pdf.cover_subtitle and output_path
 
 year: '2026'
-release: '0.9.0'
+release: '0.8.1'
 
 date:
-   v0_9_0: '2026-05-12'
+   v0_8_1: '2026-05-07'
    v0_8_0: '2026-04-06'
    v0_7_0: '2026-01-14'
    v0_6_0: '2025-09-04'