Update docs about volume snapshots on KVM (#423)

Co-authored-by: João Jandre <[email protected]>

Author: JoaoJandre

source/adminguide/storage.rst

@@ -1287,11 +1287,18 @@ is running, the global setting 'kvm.snapshot.enabled' must be set to 'True'.
 
 The Volume Snapshot creation has changed in recent versions:
 
-Under the hood, first, a full Instance Snapshot is taken - this means that during the taking of
-the Instance Snapshot the Instance will be in the "Paused" state (while RAM memory is being written to the
-QCOW2 file), which means that Instance will be unavailable from the Network point of view.
-When the Instance Snapshot is created, Instance is unpaused/resumed, the single Volume Snapshot is exported
-to the Secondary Storage, and then the Instance Snapshots is removed from the Instance.
+When the VM is running, a disk-only VM snapshot is taken, exclusively for the volume in question.
+If the VM is stopped, the volume will be converted (with qemu-img convert). The final storage location is
+determined by the ``snapshot.backup.to.secondary`` configuration; if it is false the snapshot will be copied
+to a different directory in the same primary storage as the volume; if it is true the snapshot will be copied 
+to the secondary storage. If the snapshot is being taken in a file-based storage (NFS, SharedMountPoint, Local),
+it will be copied directly to its final storage location, according to the configuration.
+
+Since 4.20.0.0, ACS supports incremental snapshots for the KVM hypervisor when using file-based storage (NFS, SharedMountPoint, Local),
+to enable incremental snapshots the ``kvm.incremental.snapshot`` configuration must be enabled. Furthermore, in order to take incremental snapshots
+the KVM host must have at least Libvirt version 7.6.0+ and qemu version 6.1+. The size of the snapshot chains
+will be determined by the ``snapshot.delta.max`` configuration, which affects both KVM and XenServer snapshots. 
+More information on the incremental snapshot feature for KVM can be found in its `specification <https://github.com/apache/cloudstack/issues/8907>`_.
 
 
 Automatic Snapshot Creation and Retention
@@ -1333,7 +1340,7 @@ incremental backups are supported, every N backup is a full backup.
 +------------------------------+------------------+------------------+-----+
 |                              | VMware vSphere   | Citrix XenServer | KVM |
 +==============================+==================+==================+=====+
-| Support incremental backup   | No               | Yes              | No  |
+| Support incremental backup   | No               | Yes              | Yes |
 +------------------------------+------------------+------------------+-----+
 
    .. note::