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The following commit(s) were added to refs/heads/main by this push:
new ff03ac3a Update value for kvm.snapshot.enabled configuration to true
in doc (#673)
ff03ac3a is described below
commit ff03ac3aad6d936a4853dd723b34ec4d3ec0891d
Author: Manoj Kumar <[email protected]>
AuthorDate: Wed Sep 2 12:31:21 2026 +0530
Update value for kvm.snapshot.enabled configuration to true in doc (#673)
---
source/adminguide/storage.rst | 31 ++++++++++++++++++++++---------
1 file changed, 22 insertions(+), 9 deletions(-)
diff --git a/source/adminguide/storage.rst b/source/adminguide/storage.rst
index c1bcb1e0..39fa72a3 100644
--- a/source/adminguide/storage.rst
+++ b/source/adminguide/storage.rst
@@ -1359,18 +1359,31 @@ How to Snapshot a Volume
KVM volume Snapshot specifics
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-In recent CloudStack versions, by default, creating a Volume Snapshot for a
running Instance is disabled
-due to a possible volume corruption in certain cases. To enable creating a
Volume Snapshots while the Instance
-is running, the global setting 'kvm.snapshot.enabled' must be set to 'True'.
+Since 4.22.0.0, creating a Volume Snapshot for a running Instance on KVM is
allowed by default; in earlier
+versions it was disabled by default. This is controlled by the global setting
``kvm.snapshot.enabled``.
+Because taking a snapshot of a running Instance can lead to volume corruption
in certain cases,
+administrators who want to require Instances to be stopped before a Volume
Snapshot can be taken should set
+this global setting to ``false``.
The Volume Snapshot creation has changed in recent versions:
-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.
+For volumes on file-based primary storage (NFS, SharedMountPoint, Local), 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). For volumes on RBD (Ceph) and CLVM
primary storage, the Volume
+Snapshot is instead taken natively by the storage layer (via the RBD ``snap
create`` operation, or the
+``managesnapshot.sh`` script for CLVM), without any interaction with the
libvirt domain; the same
+storage-side mechanism is used whether the Instance is running or stopped.
Note that on RBD, a snapshot
+taken while the Instance is running is only crash-consistent, as writes still
held in the Instance's memory
+are not flushed before the snapshot is taken.
+
+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.
+
+Snapshots of encrypted volumes are only supported while the Instance is
stopped. Taking a Volume Snapshot
+of an encrypted volume attached to a running Instance will fail.
Since 4.21.0.0, 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
