This topic describes the limitations of Cloud Backup.
Database backup
Connect your on-premises database server to an Alibaba Cloud VPC by using a leased line or VPN. This connection requires routes to the 100.64.0.0/10, 100.64.0.0/11, or 100.96.0.0/11 CIDR blocks. For more information, see Establish a VPC-to-data center connection (single-tunnel mode).
There are limits on the supported database versions, operating systems, and backup features. For more information, see Database Backup.
SAP HANA backup
You can install only one SAP HANA instance per environment. Attempting to install more than one triggers the "Installation of HANA failed" error. For more information, see Back up SAP HANA.
SAP HANA backups have the following version requirements:
Backint supports SAP HANA 1.0 SPS 09 (Revision 94) and later, but does not support SAP HANA 1.0 single-container versions.
Backint supports multitenant database containers (MDC) in SAP HANA 2.0 SPS 01 and later.
For more information, see Overview of SAP HANA backup features and FAQ about SAP HANA backup.
ECS file backup
The Windows backup client supports backups using Volume Shadow Copy Service (VSS) snapshots. However, only one VSS snapshot task can run at a time. VSS does not support features such as multi-path backup, UNC path backup, wildcards, or file exclusion.
If another application modifies a file during a backup, the data may become inconsistent. The backup does not guarantee application-level data consistency.
During a backup, if a file is in use by another process or the backup service lacks read permission for it, the backup client skips the file. The backup job is then marked as "Partially Completed".
The backup client supports only specific operating system versions. For more information, see Appendix: Operating system versions supported by the backup client.
ECS instance backup
ECS instance backup creates backups of ECS instances in CloudBox. For more information, see Alibaba Cloud services supported by CloudBox.
OSS backup
The first time you create a backup plan or attach a backup policy, Cloud Backup automatically creates a service-linked role for Cloud Backup named AliyunServiceRoleForHbrOssBackup to obtain permissions to access related resources. In the authorization dialog box that appears, grant the required permissions to the role.
Before you use Cloud Backup to protect OSS data, note the following:
Cloud Backup supports backing up and restoring buckets of the Standard and IA storage classes. It does not support backing up or restoring buckets of the Archive, Cold Archive, or Deep Cold Archive storage classes.
Cloud Backup supports backing up and restoring objects of the Standard and IA storage classes. Objects of the IA storage class are restored as objects of the Standard storage class. Cloud Backup does not support backing up or restoring objects of the Archive, Cold Archive, or Deep Cold Archive storage classes.
Cloud Backup does not support backing up or restoring the access control list (ACL) of an object.
You are charged OSS request fees for OSS API operations that Cloud Backup calls during the backup of OSS objects. These fees are charged by OSS. For more information, see Billing.
When Cloud Backup reads OSS data from IA buckets or objects for backup, you incur OSS data retrieval fees. You are charged based on the volume of retrieved data. These fees are charged by OSS. For more information, see Data processing fees.
Deleting an early backup version from the backup history does not affect the data integrity of other backup versions.
The scheduled backup plan that is enabled when you create an OSS bucket is a 30-day free trial. The plan is automatically disabled upon expiration. Switch to the paid plan promptly.
ImportantThe 30-day free trial has several key limitations: It does not support backup policies, and its source path and backup cycle are fixed. Most importantly, the trial uses an isolated backup vault that cannot be changed or merged after converting to a paid plan. Therefore, if you intend to consolidate all backups into a single vault, you should start directly with a paid plan instead of using the free trial.
When you use an OSS manifest for a backup, Cloud Backup uses the most recent manifest file from the last 7 days to improve incremental backup performance.
Generating an OSS manifest file takes time. The following limits apply:
If no OSS manifest file exists when a backup job is triggered, the job fails.
If an OSS manifest file exists when a backup job is triggered, but the file has not been updated since the last backup, the job fails.
When a backup job is triggered, the job uses only the most recently generated OSS manifest file. Files added to the bucket after the manifest is generated are backed up in the next backup cycle.
The backup interval must be at least as long as the OSS manifest generation period to ensure a new manifest file is available for each backup.
OSS backup does not support backing up buckets in CloudBox.
NAS backup
Alibaba Cloud NAS backup
Alibaba Cloud NAS backup does not support the NAS SMB ACL feature. For more information, see Back up a General-purpose NAS file system.
On-premises NAS backup
The backup client supports only specific operating system versions. For more information, see Appendix: Operating system versions supported by the backup client.
CPFS backup
The backup client supports only specific operating system versions. For more information, see Appendix: Operating system versions supported by the backup client.
On-premises file backup
The Windows backup client supports backups using Volume Shadow Copy Service (VSS) snapshots. However, only one VSS snapshot task can run at a time. VSS does not support features such as multi-path backup, UNC path backup, wildcards, or file exclusion.
If another application modifies a file during a backup, the data may become inconsistent. The backup does not guarantee application-level data consistency.
During a backup, if a file is in use by another process or the backup service lacks read permission for it, the backup client skips the file. The backup job is then marked as "Partially Completed".
The backup client supports only specific operating system versions. For more information, see Appendix: Operating system versions supported by the backup client.
VMware backup and disaster recovery
Use vCenter Web Client 6.7 or later to deploy the backup client.
The backup gateway must be able to access the vCenter server and ESXi hosts that manage the VMs to be backed up by using their FQDNs or IP addresses.
You cannot back up VMs that have existing snapshots. If you select a VM with a snapshot, the message This VM Has A Snapshot And Cannot Be Backed Up is displayed. You must manually delete the snapshot to back up the VM.
You cannot back up VMs that use shared SCSI devices because vSphere VM snapshots do not support this configuration.
The names of VMs to be backed up cannot contain the following characters:
^ ~ = ; ! / ( ) [ ] { } @ $ \ & # % +Incremental backup using Changed Block Tracking (CBT) is not supported in the following scenarios:
The hardware version of the VM is earlier than 7.
CBT is not enabled on the VM.
The VM uses a Raw Device Mapping (RDM) disk in physical compatibility mode.
The VM uses an independent disk in persistent or non-persistent mode.
The hardware version of the VM must be 10 (compatible with ESXi 5.5) or later.
VMware backup does not support VMs that use PCI passthrough or a virtual GPU (vGPU) because their underlying technologies do not support the snapshot operations required for backup.
Before you restore a VMware VM to an Alibaba Cloud ECS instance, review the following limitations for ECS instance operating systems and the VMware platform.
Windows operating systems
Limit
Description
System limits
Ensure the integrity of the file system.
Do not modify critical system files.
Ensure the system disk is not full.
The system disk capacity must be between 40 GiB and 500 GiB.
The first disk of the VM must be the system disk. Otherwise, the resulting ECS instance may fail to start.
The administrator password must be 8 to 30 characters long and contain at least three of the following character types: uppercase letters, lowercase letters, digits, and special characters. Special characters can be
( ) ` ~ ! @ # $ % ^ & * - _ + = | { } [ ] : ; ' < > , . ? /. The password cannot start with a forward slash (/).
Supported operating systems
Windows Server 2012
Windows Server 2016
Windows Server 2019
Windows Server 2022
Windows Server 2025
Unsupported items
Do not install QEMU Guest Agent (qemu-ga). Otherwise, some services required by ECS may become unavailable.
The following operating system versions are not supported:
Windows XP
Windows 8
Windows 8.1
Windows 10
Windows 11
Do not install community edition virtio drivers in Windows Server. If they are installed, remove the read-only attribute from the following files:
C:\Windows\System32\drivers\netkvm.sys
C:\Windows\System32\drivers\balloon.sys
C:\Windows\System32\drivers\vioser.sys
C:\Windows\System32\drivers\viostor.sys
C:\Windows\System32\drivers\pvpanic.sys
Linux operating systems
Limit
Description
System limits
Ensure the integrity of the file system.
Do not modify critical system files, such as files in the /sbin, /bin, and /lib* directories.
Do not modify /etc/issue*. Otherwise, ECS cannot detect the system distribution, and instance creation will fail.
Do not modify /boot/grub/menu.lst. Otherwise, the ECS instance cannot start.
Do not modify /etc/fstab. Otherwise, partitions may fail to mount, preventing the ECS instance from starting.
Do not set /etc/shadow to read-only. Otherwise, the password file cannot be modified, and instance creation will fail.
Avoid enabling SELinux by modifying the /etc/selinux/config file, as this may prevent the system from starting. If you must enable SELinux, see Enable or disable SELinux.
Ensure the system disk is not full.
The first disk of the VM must be the system disk. Otherwise, the resulting ECS instance may fail to start.
Enable the Dynamic Host Configuration Protocol (DHCP) service.
Install Xen or KVM virtualization drivers. For more information, see Install virtio drivers.
Install cloud-init to allow configuration of the hostname, NTP source, and yum repository. For more information, see Install cloud-init.
The root password must be 8 to 30 characters long and contain at least three of the following character types: uppercase letters, lowercase letters, digits, and special characters. Special characters can be
( ) ` ~ ! @ # $ % ^ & * - _ + = | { } [ ] : ; ' < > , . ? /.GRUB must be version 1.99 or later.
Supported operating systems
CentOS 6, 7, and 8
Ubuntu 10, 12, 14, 16, 17, 18, 19, and 20
Debian 7, 8, 9, and 10
SUSE 11, 12, and 15
openSUSE 13, 42, and 15
RHEL 5, 6, 7, and 8
ECS Bare Metal Instances are not compatible with some earlier operating system versions. For a list of incompatible versions and their solutions, see Some earlier operating system versions are not compatible with ECS Bare Metal Instances.
Unsupported items
Multiple network interfaces are not supported.
IPv6 addresses are not supported.
Resizing system disk partitions is not supported. Only a single root partition is supported.
Do not install QEMU Guest Agent (qemu-ga). Otherwise, some services required by ECS may become unavailable.
System disk partitions (root partitions) created across multiple disks by using Logical Volume Manager (LVM) are not supported. This configuration may cause the ECS instance to fail to start.
VMware platform
Limit
Description
vCenter version
vCenter 6.7 and later are supported. The migration gateway must have access to the vCenter server and ESXi hosts that manage the source VMs by using their FQDNs or IP addresses.
Hardware version
The hardware version of the VM must be 10 (compatible with ESXi 5.5) or later.
ECS disaster recovery
ECS disaster recovery (cloud disk async replication) has limitations regarding regions, zones, ECS instance types, cloud disks, networks, and quotas. For more information, see Limits of ECS disaster recovery (async replication).
ECS disaster recovery (continuous replication) has limitations regarding operating systems, infrastructure, databases, and applications. For more information, see Limits of ECS disaster recovery (continuous replication).
VMware VM migration
The VMware VM migration service performs a non-intrusive, agentless, full-copy migration of VMs from a VMware environment. The service uses VMware snapshots and reads disk-level data to migrate entire VMs to ECS instances. Before you migrate a VM, review the following limitations for ECS instance operating systems and the VMware platform.
Windows operating systems
Item
Description
System limits
Ensure the integrity of the file system.
Do not modify critical system files.
Ensure the system disk is not full.
The system disk capacity must be between 40 GiB and 500 GiB.
The virtual machine's first disk must be the system disk. Otherwise, the resulting ECS instance may fail to start.
The logon password for the administrator account must be 8 to 30 characters long and include at least three of the following character types: uppercase letters, lowercase letters, digits, and special characters. Special characters can be
( ) ` ~ ! @ # $ % ^ & * - _ + = | { } [ ] : ; ' < > , . ? /. The password cannot start with a forward slash (/).
Supported operating systems
Windows Server 2012
Windows Server 2016
Unsupported items
Do not install qemu-ga. Otherwise, some services that are required by ECS may become unavailable.
The following operating system versions are not supported:
Windows XP
Windows 8
Windows 8.1
Windows 10
Windows 11
Do not install community edition virtio drivers in Windows Server. If installed, remove the read-only attribute from the following files:
C:\Windows\System32\drivers\netkvm.sys
C:\Windows\System32\drivers\balloon.sys
C:\Windows\System32\drivers\vioser.sys
C:\Windows\System32\drivers\viostor.sys
C:\Windows\System32\drivers\pvpanic.sys
Linux operating systems
Item
Description
System limits
Ensure the integrity of the file system.
Do not modify critical system files, such as files in the , /bin, and /lib* directories.
Do not modify /etc/issue*. Otherwise, ECS cannot correctly detect the system distribution, and instance creation will fail.
Do not modify /boot/grub/menu.lst. Otherwise, the ECS instance cannot start.
Do not modify /etc/fstab. Otherwise, partitions may not mount correctly, and the ECS instance may fail to start.
Do not set /etc/shadow to read-only. Otherwise, the password file cannot be modified, and instance creation will fail.
Avoid enabling SELinux by modifying the /etc/selinux/config file, as this may cause the system to fail to start. If you must enable SELinux, see Enable or disable SELinux.
Ensure the system disk is not full.
The virtual machine's first disk must be the system disk. Otherwise, the resulting ECS instance may fail to start.
Enable the Dynamic Host Configuration Protocol (DHCP) service.
Install virtio drivers. For more information, see Install virtio drivers.
Install cloud-init to configure the hostname, NTP source, and yum source. For more information, see Install cloud-init.
The logon password for the root account must be 8 to 30 characters long and include at least three of the following character types: uppercase letters, lowercase letters, digits, and special characters. Special characters can be
( ) ` ~ ! @ # $ % ^ & * - _ + = | { } [ ] : ; ' < > , . ? /.The virtual machine must use GRUB version 1.99 or later.
Supported operating systems
CentOS 6, 7, and 8
Ubuntu 10, 12, 14, 16, 17, 18, 19, and 20
Debian 7, 8, 9, and 10
SUSE 11, 12, and 15
openSUSE 13, 42, and 15
RHEL 5, 6, 7, and 8
ECS Bare Metal Instances are not compatible with some earlier operating system versions. For a list of these versions and solutions, see Some earlier operating system versions are not compatible with ECS Bare Metal Instances.
Unsupported items
Multiple network interfaces are not supported.
IPv6 addresses are not supported.
Resizing the system disk partition is not supported. The system disk must contain only a single root partition.
Do not install qemu-ga. Otherwise, some services that are required by ECS may become unavailable.
LVM root partitions that span multiple disks are not supported.
VMware platform
Item
Description
vCenter version
vCenter version 6.7 or later is supported. The migration gateway must be able to access the vCenter server and the ESXi hosts that manage the source virtual machines by their FQDNs or IP addresses.
Hardware version
The VM hardware version must be 10 (compatible with ESXi 5.5) or later.
Data synchronization
Sync verification
After a sync task completes, verify data consistency between the source and destination.
After a data synchronization task completes, verify the data at the destination. If you delete the source data without first verifying the data at the destination, you are solely responsible for any resulting data loss.
Operating system version limits
The backup client supports only specific operating system versions. For more information, see Appendix: Operating system versions supported by the backup client.
Appendix: Supported operating systems for the backup client
The backup client does not support 32-bit operating systems or Windows Server versions earlier than 2008. Ensure your system meets these requirements.
Linux operating systems
Category | Description |
Supported OS versions |
|
Unsupported OS versions |
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Windows operating systems
Category | Description |
Supported OS versions |
|
Unsupported OS versions |
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