CloudWatch metrics that are useful for managing Neptune backup storage

BackupRetentionPeriodStorageUsed represents the amount of backup storage used, in bytes, for storing continuous backups at the current time. This value depends on the size of the cluster volume and the amount of changes you make during the retention period. However, for billing purposes it doesn't exceed the cumulative cluster volume size during the retention period. For example, if your cluster's VolumeBytesUsed size is 107,374,182,400 bytes (100 GiB), and your retention period is two days, the maximum value for BackupRetentionPeriodStorageUsed is 214,748,364,800 bytes (100 GiB + 100 GiB).

SnapshotStorageUsed represents the amount of backup storage used, in bytes, for storing manual snapshots beyond the backup retention period. Manual snapshots don't count against your snapshot backup storage while their creation timestamp is within the retention period. All automatic snapshots also don't count against your snapshot backup storage. The size of each snapshot is the size of the cluster volume at the time you take the snapshot. The SnapshotStorageUsed value depends on the number of snapshots you keep and the size of each snapshot. For example, suppose you have one manual snapshot outside the retention period, and the cluster's VolumeBytesUsed size was 100 GiB when that snapshot was taken. The amount of SnapshotStorageUsed is 107,374,182,400 bytes (100 GiB).

TotalBackupStorageBilled represents the sum, in bytes, of BackupRetentionPeriodStorageUsed and SnapshotStorageUsed, minus an amount of free backup storage, which equals the size of the cluster volume for one day. The free backup storage is equal to the latest volume size. For example if your cluster's VolumeBytesUsed size is 100 GiB, your retention period is two days, and you have one manual snapshot outside the retention period, the TotalBackupStorageBilled is 214,748,364,800 bytes (200 GiB + 100 GiB - 100 GiB).