{{ $t('productDocDetail.updateTime') }}: 2025-12-17

Hot Standby (Hot backup) migration utilizes CDP (Continuous Data Protection) backup technology to continuously transfer source data to the target machine via the SCMP. By leveraging high-frequency data replication, this approach minimizes service interruption. While the source runs normally, the target machine remains in a booted OS-loaded state. During the final switchover phase, the target rapidly starts up using the predefined IP. This method is typically applied in scenarios requiring minimal migration downtime.

Applicable Scenarios

1. Hot Standby Migration stores source host data on the SCMT through CDP backup, which demands higher storage capacity from the platform.
2. Prior to service switchover, the target VM remains in an OS-loaded state, significantly reducing OS transition time during migration. The actual switchover typically completes within approximately one minute, though the total downtime depends on the service startup duration.

Migration Process

The migration process of the HA backup migration mode in SCMT is as follows:

The source host installs the migration agent, and the migration tool has two modes: active and passive.

• In the active mode, the migration agent at the source actively connects to the CMP and receives tasks issued by the SCMT.

• In the passive mode, SCMT will take the initiative to connect the source machine migration agent to issue migration tasks.

2. Perform CDP backup on the entire source machine and store the backup on the SCMT.

3. Manually create the destination virtual machine, manually mount the bare metal restore ISO file and power on the VM. Configure the IP address to connect to the SCMT.

4. Create a CDP backup plan, and SCMT will sync the source machine's CDP backup to the destination virtual machine in real-time.

5. After synchronizing the data, the destination machine is ready and booting OS.

6. Stop the source application service, but do not shut down, and execute the HA backup switch plan.

7. The destination virtual machine starts compatibility processing and automatically installs performance optimization tools(vmTools).

8. The destination virtual machine restarts and takes over the production.

Migration Time

The initial synchronization only transfers the actual used data blocks within the virtual machine's disk, not the entire provisioned capacity. For instance, if a VM has a provisioned disk of 100 GB but only 50 GB is utilized, the initial sync will transfer approximately 50 GB of data. Subsequent replications are incremental, capturing only the data blocks that have changed since the last sync. Following the final incremental sync, a planned service cutover is required. This involves stopping the services on the source machine and redirecting operations to the target. For Hot Standby Migration, the service interruption during this cutover window is typically around 1 minutes.

No.	Migration Phase	Tasks	Duration / Impact
1	Pre-Migration Setup	1.1 Deploy SCMT Server  (10 min) 1.2 Install Agent on all source machines (2 min/machine) 1.3 Create CDP Backup for source machines (Duration depends on data volume) 1.4 Create Virtual Machines on target (2 min/machine)	Duration: approximately 30 minutes Impact during backup: • Agent CPU usage: < 3% • Agent Memory peak: < 260 MB
2	Data Replication	1.1 Create CDP backup on source; data transferred to migration server via agent. 2.2 Manually create target VM on destination, mount bare metal recovery boot media, start it up, and configure IP for communication with the migration tool. 2.3 Create an HA (High Availability) hot-standby plan for the target VM. 2.4 Source VM data stream is pushed in real-time from the migration server to the target. 2.5 After full data sync, the target VM is ready: has VMTools automatically injected, compatibility processing complete, and is in a boot-loading state	Duration: Total Data Volume / Migration Speed • Max speed: 100 MB/s (1 GbE), 500 MB/s (10 GbE) Source Resource Utilization: - Agent CPU usage: < 3% - Agent Memory peak: < 260 MB - Recommended free memory on source: > 1 GB - Default source storage performance cap: 30% (Queue Depth: 4) - Adjustable - Default source network bandwidth cap: 300 Mbps - Adjustable
3	Service Cutover	3.1 Issue the HA hot-standby switchover task. 3.2 Stop application services on the source machine (without shutting it down) (~10 seconds). 3.3 Activate the target VM to officially take over services (~20-30 seconds).	Duration: < 1 minute Impact: Source services stopped.

Resumable Transfer

CDP Backup Phase

1. During Full Backup:

• Network interruption < 15 min: The backup task is unaffected. Incremental data will automatically resume syncing once the network is restored.

• Network interruption > 15 min: The backup task fails. Incremental data will automatically resume syncing once the network is restored.

• Source or Server reboot/shutdown: The backup task fails. A new full backup will automatically restart after the source system recovers.

2. During CDP Protection:

• Network interruption > 2 min or log cache full: The system switches to incremental backup mode. After network recovery, an incremental backup is performed first, followed by a return to continuous CDP protection.

• Source reboot/shutdown: CDP protection fails. After the source system recovers, an incremental backup is performed first, followed by a return to continuous CDP protection.

• Server reboot/shutdown: There is no impact on source services. After the server recovers, an incremental backup is performed first, followed by a return to continuous CDP protection.

Hot-Standby Replication Phase

• Network interruption < 15 min: The replication task is suspended with no impact on the source. Incremental data will automatically resume syncing once the network is restored.

• Network interruption > 15 min: The replication task fails. The hot-standby task must be manually recreated after the network is restored.

• Server reboot/shutdown: The replication task fails. The hot-standby task must be manually recreated after the server recovers.