docs(bls): warning (scaleway#4141)

Author: nerda-codes

storage/block/api-cli/managing-a-volume.mdx

@@ -64,6 +64,10 @@ Then, check that the volume is available, format it, and mount it following the
 
 Formatting your volume prepares it for storing files.
 
+<Message type="important">
+ The procedure below describes how to format your volume using the `mkfs` command, which will **erase all data on the volume**.
+</Message>
+
 1. Create a file system with the following command. This command uses the `ext4` file system, though you can choose another if you prefer.
     ```
     # Make sure that you replace `/dev/sdX` with the name of your volume