Added upgrade guide for release-8

Signed-off-by: Rinku Kothiya <[email protected]>

docs/Upgrade-Guide/README.md

@@ -4,6 +4,7 @@ Upgrading GlusterFS
 
 If you are using GlusterFS version 3.10.x or above, you can upgrade it to the following:
 
+-   [Upgrading to 8](./upgrade_to_8.md)
 -   [Upgrading to 7](./upgrade_to_7.md)
 -   [Upgrading to 6](./upgrade_to_6.md)
 -   [Upgrading to 5](./upgrade_to_5.md)

docs/Upgrade-Guide/upgrade_to_8.md

@@ -0,0 +1,42 @@
+# Upgrade procedure to Gluster 8, from Gluster 7.x, 6.x, 5.x, 4.1.x, and 3.12.x
+
+We recommend reading the [release notes for 8.0](../release-notes/8.0.md) to be
+aware of the features and fixes provided with the release.
+
+> **NOTE:** Upgrade procedure remains the same as with 4.1.x release
+
+Refer, to the [Upgrading to 4.1](./upgrade_to_4.1.md) guide and follow
+documented instructions, replacing 8 when you encounter 4.1 in the guide as the
+version reference.
+
+### Major issues
+
+1. The following options are removed from the code base and require to be unset
+before an upgrade from releases older than release 4.1.0,
+- features.lock-heal
+- features.grace-timeout
+
+To check if these options are set use,
+
+```console
+# gluster volume info
+```
+
+and ensure that the above options are not part of the `Options Reconfigured:`
+section in the output of all volumes in the cluster.
+
+If these are set, then unset them using the following commands,
+
+```console
+# gluster volume reset <volname> <option>
+```
+
+**NOTE:** Failure to do the above may result in failure during online upgrades,
+and the reset of these options to their defaults needs to be done **prior** to
+upgrading the cluster.
+
+### Deprecated translators and upgrade procedure for volumes using these features
+
+[If you are upgrading from a release prior to release-6 be aware of deprecated xlators and functionality](https://docs.gluster.org/en/latest/Upgrade-Guide/upgrade_to_6/#deprecated-translators-and-upgrade-procedure-for-volumes-using-these-features). 
+
+

mkdocs.yml

@@ -91,6 +91,7 @@ nav:
 - Upgrade-Guide:
   - Upgrade-Guide Index: Upgrade-Guide/README.md
   - Op-version: Upgrade-Guide/op_version.md
+  - Upgrade to 8: Upgrade-Guide/upgrade_to_8.md
   - Upgrade to 7: Upgrade-Guide/upgrade_to_7.md
   - Upgrade to 6: Upgrade-Guide/upgrade_to_6.md
   - Upgrade to 5: Upgrade-Guide/upgrade_to_5.md