High-frequency snapshots have the following caveats and limitations:
- Interoperability between high-frequency snapshots and VADP on same VM. If a VM is protected using VMware Cloud DR 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 Cloud DR is replicating a high-frequency snapshot, this snapshot task pauses and retries after a few seconds. VMware Cloud DR will continue the snapshot replication from the point of interruption. However, if this interruption occurs near the end of a high-frequency snapshot task, VMware Cloud DR might be required to perform a full ingest, which can take a long time.
Best Practice: If you are using both a third party backup solution that uses VADP and VMware Cloud DR 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 Cloud DR during steady state replications, as compared to during initial seeding.
- Interoperability limitation between VMware Cloud DR high-frequency snapshots and VMware HCX. You cannot use VMware HCX to perform a bulk migration or a replication assisted vMotion (RAV) for set of VMs on a VMware Cloud DR 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 Cloud DR 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 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 Cloud DR) 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 Cloud DR, 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 (restore destination 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.
- Mixed clusters not supported (on-premises protected sites only). High-frequency snapshots function at the host-level, so if you have an on-premises protected site vSphere cluster where some ESXi hosts are running 7.0 Update 3 and some are not, then enabling high-frequency snapshots for VMs on that cluster is not supported.
- Protection group can only have one snapshot type. A protection group can only be configured for one snapshot type: standard-frequency, high-frequency, or quiesced. 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 can 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 back the protection group to take standard-frequency snapshots.
- 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 subsquent 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.
- Under certain scenarios when multiple failback or restore operations are performed on the same VM, a non-incremental restore may be required. If you perform a failback from a snapshot (or a single VM restore), and then perform a subsequent failback from a snapshot that existed at time of the first failback, VMware Cloud DR requires a longer, non-incremental restore to complete the failback. For example, if you perform a failback operation from a protection group that has 5 snapshots, and failback using snapshot 5, if you then perform a second failback using snapshot number 3, the system requires a longer, non-incremental restore.
- 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 Cloud DR 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 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.