Keep log pvc when release uninstalled (#295)

Signed-off-by: Edward Zeng <jie.zeng@zilliz.com>

Author: LoveEachDay

charts/milvus/Chart.yaml

@@ -3,7 +3,7 @@ name: milvus
 appVersion: "2.0.0"
 kubeVersion: "^1.10.0-0"
 description: Milvus is an open-source vector database built to power AI applications and vector similarity search.
-version: 3.0.2
+version: 3.0.3
 keywords:
   - milvus
   - elastic

charts/milvus/values.yaml

@@ -108,22 +108,23 @@ log:
 
   persistence:
     mountPath: "/milvus/logs"
-    ## If true, alertmanager will create/use a Persistent Volume Claim
+    ## If true, create/use a Persistent Volume Claim
     ## If false, use emptyDir
     ##
     enabled: false
-    annotations: {}
-    #  helm.sh/resource-policy: keep
+    annotations:
+      helm.sh/resource-policy: keep
     persistentVolumeClaim:
       existingClaim: ""
       ## Milvus Logs Persistent Volume Storage Class
       ## If defined, storageClassName: <storageClass>
       ## If set to "-", storageClassName: "", which disables dynamic provisioning
       ## If undefined (the default) or set to null, no storageClassName spec is
       ##   set, choosing the default provisioner.
+      ## ReadWriteMany access mode required for milvus cluster.
       ##
       storageClass:
-      accessModes: ReadWriteOnce
+      accessModes: ReadWriteMany
       size: 10Gi
       subPath: ""