Caveats for High-frequency Snapshots

High-frequency snapshots have several caveats and limitations.

• Interoperability between high-frequency snapshots and VADP on the same VM. If a VM is protected using VMware Live Cyber Recovery and enabled for high-frequency snapshots, there might be potential interruptions in snapshot replication if the same VM is also being backed up by a third party backup solution that uses VMware APIs for Data Protection (VADP). When the third party backup solution creates or deletes a VADP backup at the same time VMware Live Cyber Recovery is replicating a high-frequency snapshot, this snapshot task pauses and retries after a few seconds. VMware Live Cyber Recovery will continue the snapshot replication from the point of interruption.
  Best Practice: If you are using both a third party backup solution that uses VADP and VMware Live Cyber Recovery snapshots to protect the same VM, first create a standard-frequency snapshot of the VM for initial seeding. Then, convert the protection group to high-frequency snapshots and resume the snapshot schedule. Interruptions from third party backup solution that uses VADP are less likely to require a full ingest by VMware Live Cyber Recovery during steady state replications, as compared to during initial seeding.
• VMware Tools AppInfo plug-in is not supported. If you are protecting a VM with VMware Tools installed with AppInfo enabled, collected application data is stored in the VMX file of the VM, causing it to expand to >55 KB. Because VMware Live Cyber Recovery does not allow backup of VMX files that are >55 KB, snapshot replication fails. To avoid this situation, deactivate the AppInfo plug-in VMware Tools for the VM.
• Interoperability limitation between high-frequency snapshots and VMware HCX. You cannot use VMware HCX to perform a bulk migration or a replication assisted vMotion (RAV) for the set of VMs on a VMware Live Cyber Recovery protected SDDC, if those VMs are also being replicated using high-frequency snapshots. However, HCX bulk migrations and RAV are supported if the VMs being migrated to (or from) a VMware Live Cyber Recovery protected site are not being replicated with high-frequency snapshots.
• Software Requirement. High-frequency snapshots are only supported on protected sites running vSphere 7.0 Update 3 or higher and protected SDDCs running version 1.16 or higher. For the latest release information on vSphere 7.0 Update 3, see these product Release Notes.
• vSphere Virtual Machine Encryption not supported. High-frequency snapshots use a temporary external snapshot file to capture information that gets overwritten after a snapshot is taken. This external snapshot file is not protected by vSphere Virtual Machine Encryption and thus impacts data confidentiality of captured disk blocks. For these reasons, VMs with vSphere encryption enabled are not supported for high-frequency snapshots.
• Special characters not supported. High-frequency snapshots are not supported in vSphere environments that use non-ASCII or special characters in inventory object names (such as VMs, VM templates, hosts, clusters, networks, datastores).
• High-frequency snapshots cannot be enabled on protection groups if there are vSphere snapshot types present. Protection Groups with VMs where existing vSphere (non-VMware Live Cyber Recovery) snapshots are present cannot be enabled for high-frequency snapshots. This limitation is because Change Block Tracking (CBT) cannot be enabled when vSphere snapshots exist at the time high-frequency snapshots are enabled. However, vSphere snapshots can be taken after the first high-frequency snapshot completes. If you have VMs with existing snapshots not taken by VMware Live Cyber Recovery, you can delete the existing snapshots on disks attached to the VM, or consolidate them so none are present at the time a snapshot is taken. Once you have deleted or consolidated the existing vSphere snapshots, high-frequency snapshots can be enabled and new vSphere Snapshots can be created for a VM.
• Restoring a deleted VM fails when restore destination site is non-compatible with high-frequency snapshots. If you attempt to restore or fail back a deleted VM from high-frequency snapshot, and none of the hosts on the cluster are compatible with high-frequency snapshots (destination site must be on vSphere 7.0 Update 3), the VM is created but is not fully restored. In this situation, the VM is unusable. If this situation occurs, make sure that at least one host in the cluster's resource pool is compatible with high-frequency snapshots, and then retry the VM restore operation. In this case, you can only perform a single VM restore. You cannot retry the failback.
• Protection group can only have one snapshot type. A protection group can only be configured for one snapshot type: standard-frequency or high-frequency. You cannot mix snapshot types in a protection group.
• VMs must be part of a cluster. The enablement of high-frequency snapshots of VMs and their disks is only supported for VMs that are part of a cluster, not on a standalone host. If you have standalone hosts, place them in a cluster. You can then add VMs on the host to protection groups and schedule high-frequency snapshots.
• Converting protection groups from high-frequency snapshots to standard-frequency snapshots not supported. Once a protection group is enabled for high-frequency snapshots, you cannot revert that protection group to take standard-frequency snapshots again.
• VMs with mixed snapshot types. If a VM belongs to a protection group configured for either standard-frequency snapshots or quiesced snapshots, and the same VM is captured in another snapshot from a different protection group configured for high-frequency snapshots, all subsequent snapshots for that VM are captured as high-frequency snapshots.
• 'Unprotect' a VM from a high-frequency snapshot protection group. If you have a VM that previously belonged to a protection group with high-frequency snapshots enabled and you want to ‘unprotect’ the VM, see Detach High-frequency Snapshot from VMs.
• VMs using VMware vSphere Virtual Volumes (vVols) not supported. VMs that use vVols are not supported for high-frequency snapshots.
• Not supported with vSphere Replication and array-based replication using VMware Site Recovery Manager (SRM). High-frequency snapshots do not support replicating VMs using vSphere Replication or array-based replication with VMware Site Recovery Manager (SRM), if those VMs are also being protected by VMware Live Cyber Recovery high-frequency snapshots.
• Increased VM memory overhead for vSphere Distributed Resource Scheduler (DRS)-enabled clusters (on-premises protected sites only). Using high frequency snapshots increases the VM memory overhead for protected VMs for on-premises protected vSphere sites. If you have manually adjusted the VM memory overhead setting, then using high-frequency snapshots might require a change to the manual setting. For example, for a VM with a large number of disks, the memory overhead specified might be insufficient. If needed, contact VMware support to adjust this setting.
• If vSphereBackupNFC is set manually, it must be set to use a routable network interface. If you change the vSphere backup network setting vSphereBackupNFC, ensure that it is set to use a routable network interface, or high-frequency snapshots won't work.