CLoudwatch EBS卷磁盘空间警报

Question

嗨，我正在尝试为Linux Ec2实例的磁盘使用率（/ apps / external / 4-sdf）-EBS卷创建cloudwatch警报，但是即使有足够的空间，我也会收到警报被触发：请问让我知道此警报有什么问题吗？

  ApplicationVolumeDiskSpaceTooLowAlarm:
    Type: "AWS::CloudWatch::Alarm"
    Condition : CreateEc2DashBoard
    Properties:
      AlarmDescription: !Sub "${AppEc2Stack} - EBS /apps/external/4 Volume - application volume has low free space"
      AlarmName: !Sub "EC2-ApplicationVolumeDiskSpaceTooLowAlarm-${AppEc2Stack}"
      AlarmActions:
        - !Ref NetcoolSNS
      ComparisonOperator: LessThanOrEqualToThreshold 
      Dimensions:
        - Name: AutoScalingGroupName
          Value: 
                  Fn::ImportValue:
                    !Sub ${AppEc2Stack}-AsgId
        - Name: Volume
          Value: "/apps/external/4"
      EvaluationPeriods: 2
      MetricName: "LogicalDisk % Free Space"
      Namespace: "CWAgent"
      Period: 300
      Threshold: 5 
      Statistic: Average
      TreatMissingData: !Ref CWAlarmTreatMissingData # "breaching"