Disk backup overview updates

Author: AbhishekMallick-MS

articles/backup/disk-backup-overview.md

@@ -2,7 +2,7 @@
 title: Overview of Azure Disk Backup
 description: Learn about the Azure Disk backup solution.
 ms.topic: conceptual
-ms.date: 07/21/2023
+ms.date: 08/17/2023
 ms.service: backup
 author: AbhishekMallick-MS
 ms.author: v-abhmallick
@@ -84,6 +84,15 @@ The snapshots created by Azure Backup are stored in the resource group within yo
 
 The number of recovery points is determined by the Backup policy used to configure backups of the disk backup instances. Older block blobs are deleted according to the garbage collection process as the corresponding older recovery points are pruned.
 
+## Why do I see more snapshots than my retention policy?
+
+If a retention policy is set as *1*, you can find two snapshots. This configuration ensures that at least one latest recovery point is always present in the vault, if all subsequent backups fail due to any issue. This causes the presence of two snapshots.
+
+So, if the policy is for *n* snapshots, you can find *n+1* snapshots at times. Further, you can even find *n+1+2* snapshots if there is a delay in deletion of recovery points whose retention period is over (garbage collection). This can happen at rare times when:
+
+- You clean up snapshots, which are past retentions.
+- The garbage collector (GC) in the backend is under heavy load.
+
 ## Next steps
 
 [Azure Disk Backup support matrix](disk-backup-support-matrix.md)