collect data from all volumes which attached to the instance
if you run on an ec2-instance, you probably don't have to specify -instance-id & -region
if you run on an ec2-instance and the instance is associated with an appropriate IAM Role, you probably don't have to specify -access-key-id & -secret-access-key
the credential provided manually or fetched automatically with IAM Role, should have the policy that includes an action, cloudwatch:GetMetricStatistics and ec2:DescribeVolumes