DX-49550: Clarify image tag usage documentation.

- Clarify documentation to provide recommended image tag usage.

Change-Id: Iaad12fee063f252dc0bec5e08a1ed5b95b1b431b

Author: ryantse

charts/dremio_v2/docs/Values-Reference.md

@@ -22,7 +22,9 @@ Type: String
 
 By default, the value is set to `latest`.
 
-It is **strongly** recommended to pin the version of Dremio that we are deploying by setting the `imageTag` to a precise version and not leave the value as latest. Since Dremio versions are not backwards compatible, leaving it as latest may automatically upgrade dremio during pod creation.
+The `imageTag` refers to the tag/version of the container image for Dremio.
+
+***Note***: It is **strongly** recommended to pin the version of Dremio that we are deploying by setting the `imageTag` to a precise version and not leave the value as latest. If you are directly consuming Dremio's images from Docker Hub, when specifying which version to use, it is recommended to use the full version tag in the form `X.Y.Z` (i.e. `21.1.0`), as image tags in the form `X.Y` (i.e. `21.1`) are continually updated with the latest patch version released. Since Dremio versions are not backwards compatible, leaving it as latest or in the form `X.Y` may automatically upgrade Dremio during pod creation.
 
 #### `imagePullSecrets`
 

charts/dremio_v2/docs/setup/Important-Setup-Considerations.md

@@ -2,7 +2,7 @@
 
 As part of setting up a Dremio cluster on Kubernetes, there are a number of important considerations that we recommend you review before deploying your cluster. Some of these values have an impact on the performance of your cluster and should be adjusted to your needs.
 
-* `imageTag`: As part of setup, this value should be updated to reference the exact version of Dremio you wish to deploy, i.e. `4.7.0`.
+* `imageTag`: As part of setup, this value should be updated to reference the exact version of Dremio you wish to deploy, i.e. `4.7.0`. If you are directly consuming Dremio's images from Docker Hub, when specifying which version to use, it is recommended to use the full version tag in the form `X.Y.Z` (i.e. `21.1.0`), as image tags in the form `X.Y` (i.e. `21.1`) are continually updated with the latest patch version released.
 * `distStorage.type`: By default, the `distStorage.type` is set to `local`. This **must** be changed prior to production use. We do not recommend users use local distributed storage as part of a production setup.
 * `volumeSize` and `storageClass`: The size and type of volume used for Dremio has a direct impact on performance. In most Kubernetes providers, volume size has a direct impact on the performance in IOPS and read/write speeds. It is important to check your Kubernetes provider to determine how volume size impacts the performance of your disk.
 * `executor.cloudCache.storageClass`: Dremio C3 was designed to be used with performant NVMe storage. By default, the chart utilizes the default storage class that is configured on the Kubernetes cluster. For the major Kubernetes providers, NVMe storage is often available on appropriately sized nodes. We recommend utilizing a local storage provisioner to unlock the benefits of NVMe storage available on the physical Kubernetes nodes. For more information, see the [Kubernetes Special Interest Group for Local Static Provisioner](https://github.com/kubernetes-sigs/sig-storage-local-static-provisioner).

charts/dremio_v2/values.yaml

@@ -2,9 +2,15 @@
 #
 # It is *highly* recommended to update the version tag to
 # the version that you are using. This will ensure that all
-# the pods are using the same version of the software.
+# the pods are using the same version of the software. If
+# you are directly consuming Dremio's images from Docker Hub,
+# when specifying which version to use, it is best to use the
+# full version tag in the form X.Y.Z (i.e. 21.1.0), as image
+# tags in the form X.Y (i.e. 21.1) are updated with the latest
+# patch version released.
 #
-# Using latest will cause Dremio to potentially upgrade versions
+# Using the image tag latest or in the form X.Y
+# will potentially cause Dremio to upgrade versions
 # automatically during redeployments and may negatively impact
 # the cluster.
 image: dremio/dremio-oss