TASK: add note that volume servers need restart after changing the master toml

Cloud-Tier.md

@@ -55,6 +55,7 @@ Compared to direct S3 storage, this is both faster and cheaper!
 Multiple s3 buckets are supported. Usually you just need to configure one backend.
 
 ```
+# The storage backends are configured on the master, inside master.toml
 [storage.backend]
 	[storage.backend.s3.default]
 	enabled = true
@@ -72,6 +73,9 @@ Multiple s3 buckets are supported. Usually you just need to configure one backen
 
 ```
 
+After changing the master config, you need to **restart the volume servers** so that they pull the updated configuration
+from the master. If you forget to do this, you'll get an error message about no storage backends being configured.
+
 After this is configured, you can use this command to upload the .dat file content to the cloud.
 
 ```