From c9aae60db860ed3080f16be615552be602f47950 Mon Sep 17 00:00:00 2001 From: Abhisar Sinha <63767682+abh1sar@users.noreply.github.com> Date: Wed, 24 Sep 2025 13:24:50 +0530 Subject: [PATCH 1/2] vm pause documentation --- source/adminguide/virtual_machines.rst | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/source/adminguide/virtual_machines.rst b/source/adminguide/virtual_machines.rst index 545e44d20a..ceb58444e8 100644 --- a/source/adminguide/virtual_machines.rst +++ b/source/adminguide/virtual_machines.rst @@ -1265,6 +1265,8 @@ When the snapshotting is complete, the Instance is thawed. You can use this functionality on Instances with raw block storages (E.g. Ceph/SolidFire/Linstor). +.. _Disk-only-File-based-Storage-Instance-Snapshots-on-KVM: + Disk-only File-based Storage Instance Snapshot on KVM ----------------------------------------------------- @@ -1298,6 +1300,25 @@ Limitations on Instance Snapshots managed by CloudStack. Any Snapshots that you make directly on the hypervisor will not be tracked in CloudStack. +Pause During Live Instance Snapshots on KVM +------------------------------------------- + +When creating **Instance Snapshots with Memory**, CloudStack uses Libvirt’s +*domain snapshot* API to create an Intlrnal Snapshot that includes Memory. +The guest’s memory state is written directly into the root volume’s QCOW2 file. +This causes the instance to pause for the duration of the memory dump. The pause +time is typically much longer than with VMware snapshots, but this is a limitation +with Internal Snapshots in Libvirt. + +**Instance Snapshots without Memory** has seen significant improvements since Cloudstack 4.21 with the +:ref:`Disk-only-File-based-Storage-Instance-Snapshots-on-KVM` feature for NFS and local storage. +Pre 4.21, the Instance would be frozen for the entire duration of the snapshot create operation. +Since 4.21, the Instance is only frozen during the checkpointing operation, which is significantly less. + +Users looking for the Instance Snapshot feature in KVM are recommended to use the +:ref:`Disk-only-File-based-Storage-Instance-Snapshots-on-KVM` feature, if the pause duration is a concern. +App consistent snapshots can be created by using the ``quiescevm`` parameter with pre and post-freeze hooks. +The Instance should have Qemu Guest Agent installed for this to work. Configuring Instance Snapshots ------------------------------ From 4b74f72d1926b57a9f178c5450528591a4f9f8d9 Mon Sep 17 00:00:00 2001 From: Abhisar Sinha <63767682+abh1sar@users.noreply.github.com> Date: Wed, 24 Sep 2025 14:26:29 +0530 Subject: [PATCH 2/2] Update typo in source/adminguide/virtual_machines.rst Co-authored-by: Wei Zhou --- source/adminguide/virtual_machines.rst | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/source/adminguide/virtual_machines.rst b/source/adminguide/virtual_machines.rst index ceb58444e8..9280aefcc9 100644 --- a/source/adminguide/virtual_machines.rst +++ b/source/adminguide/virtual_machines.rst @@ -1304,7 +1304,7 @@ Pause During Live Instance Snapshots on KVM ------------------------------------------- When creating **Instance Snapshots with Memory**, CloudStack uses Libvirt’s -*domain snapshot* API to create an Intlrnal Snapshot that includes Memory. +*domain snapshot* API to create an Internal Snapshot that includes Memory. The guest’s memory state is written directly into the root volume’s QCOW2 file. This causes the instance to pause for the duration of the memory dump. The pause time is typically much longer than with VMware snapshots, but this is a limitation