This topic describes the limits of Cloud Backup.
Database backup
Your on-premises database server must be connected to an Alibaba Cloud virtual private cloud (VPC) through a leased line or VPN, and the connection must use routes within 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).
Limits apply to the supported database versions, operating systems, and backup features. For more information, see Database Backup.
SAP HANA backup
Only one SAP HANA instance can be installed in each environment. Otherwise, an "Installation of HANA failed" error message is displayed. For more information, see Back up SAP HANA.
The following version requirements apply to SAP HANA backups:
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 that use Volume Shadow Copy Service (VSS) snapshots. However, only one VSS snapshot task can run at a time. When you use VSS, features such as multi-path backup, UNC path backup, wildcard character matching, or file exclusion are not supported.
If a file is modified by another application 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 does not have read permission for the file, the file is skipped. The backup job status is then displayed 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
You can use ECS instance backup to back up 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 overview.
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. We recommend that you switch to the paid plan promptly.
ImportantThe free trial plan has limitations. You cannot edit the source path and backup cycle. Each free trial plan uses a separate backup vault. You cannot change the backup vault after you switch to the paid plan. If you plan to back up all your data to the same backup vault in the future, do not use the free trial plan.
For backups that use an OSS manifest, Cloud Backup uses the most recent manifest file from the last seven 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. New files added to the manifest file after the backup is complete are backed up in the next backup cycle.
The backup interval must be greater than or equal to the OSS manifest generation period. This ensures that a new OSS 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 currently 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 that use Volume Shadow Copy Service (VSS) snapshots. However, only one VSS snapshot task can run at a time. When you use VSS, features such as multi-path backup, UNC path backup, wildcard character matching, or file exclusion are not supported.
If a file is modified by another application 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 does not have read permission for the file, the file is skipped. The backup job status is then displayed 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
Deploy the backup client using vCenter Web Client 6.7 or later.
The backup gateway must have access to the vCenter server and ESXi hosts that manage the backup VMs through 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 appears. 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 following characters are not allowed in the names of VMs to be backed up:
`! # $ % & ( ) + / ; = @ [ \ ] ^ { } ~`
Incremental backup using Changed Block Tracking (CBT) is not supported in the following scenarios:
The hardware version of the VM is earlier than 7.
Changed Block Tracking (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 VM must have hardware version 10 (compatible with ESXi 5.5) or later.
You cannot use the VMware backup feature to back up or restore encrypted VMs.
VMware backup does not support VMs that use PCI passthrough or virtual GPU (vGPU) because the underlying implementation of these technologies does not support snapshot operations.
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.
Check the remaining space on the system disk to ensure that it is not full.
The system disk capacity must be within the range of 40 GiB to 500 GiB.
Only VMs whose first disk is the system disk are supported. If the first disk is not the system disk, the resulting ECS instance may fail to start.
The logon password of the administrator account must be 8 to 30 characters in length 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-ga in the system. 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* folders.
Do not modify /etc/issue*. Otherwise, ECS cannot correctly detect the system distribution, which causes the instance creation to fail.
Do not modify /boot/grub/menu.lst. Otherwise, the ECS instance cannot be started.
Do not modify /etc/fstab. Otherwise, abnormal partitions cannot be loaded, and the ECS instance cannot be started.
Do not set /etc/shadow to read-only. Otherwise, the password file cannot be modified, which causes the instance creation to fail.
We do not recommend that you enable SELinux by modifying the /etc/selinux/config file. Otherwise, the system may fail to start. If you must enable SELinux, see Enable or disable SELinux.
Check the remaining space on the system disk to ensure that it is not full.
Only VMs whose first disk is the system disk are supported. If the first disk is not the system disk, 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 ensure that the hostname, NTP source, and yum source can be configured. For more information, see Install cloud-init.
The logon password of the root account must be 8 to 30 characters in length and contain at least three of the following character types: uppercase letters, lowercase letters, digits, and special characters. Special characters can be
( ) ` ~ ! @ # $ % ^ & * - _ + = | { } [ ] : ; ' < > , . ? /.GRUB version requirement: For Linux operating systems, you must update GRand Unified Bootloader (GRUB) to version 1.99 or later.
Supported operating systems
CentOS 6, 7, 8
Ubuntu 10, 12, 14, 16, 17, 18, 19, 20
Debian 7, 8, 9, 10
SUSE 11, 12, 15
openSUSE 13, 42, 15
RHEL 5, 6, 7, 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 system disk partitions is not supported. Only a single root partition is supported.
Do not install qemu-ga in the system. Otherwise, some services required by ECS may become unavailable.
System disk partitions (root partitions) built across disks using Logical Volume Manager (LVM) are not supported. Otherwise, the ECS instance may fail to start.
VMware platform
Limit
Description
vCenter version
vCenter 6.7 and later are supported. The migration gateway must be able to access the vCenter server and ESXi hosts that manage the backup VMs using their FQDNs or IP addresses.
Hardware version
The VM hardware version must be 10 (corresponding to ESXi 5.5) or later.
ECS disaster recovery
ECS disaster recovery (async replication) is subject to limitations on regions, zones, ECS instance types, disks, networks, and quotas. For more information, see Limits of ECS disaster recovery (async replication).
ECS disaster recovery (continuous replication) is subject to limitations on operating systems, infrastructure, databases, and applications. For more information, see Limits of ECS disaster recovery (continuous replication).
VMware VM migration
The VMware virtual machine (VM) migration service performs a non-intrusive, agentless, full-copy migration of VMs from a VMware environment. The service uses VMware snapshots and reads data at the disk level 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.
Check the remaining space on the system disk to ensure that it is not full.
The system disk capacity must be within the range of 40 GiB to 500 GiB.
Only VMs whose first disk is the system disk are supported. If the first disk is not the system disk, the resulting ECS instance may fail to start.
The logon password of the administrator account must be 8 to 30 characters in length 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
Unsupported items
Do not install qemu-ga in the system. 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
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* folders.
Do not modify /etc/issue*. Otherwise, ECS cannot correctly detect the system distribution, which causes the instance creation to fail.
Do not modify /boot/grub/menu.lst. Otherwise, the ECS instance cannot be started.
Do not modify /etc/fstab. Otherwise, abnormal partitions cannot be loaded, and the ECS instance cannot be started.
Do not set /etc/shadow to read-only. Otherwise, the password file cannot be modified, which causes the instance creation to fail.
We do not recommend that you enable SELinux by modifying the /etc/selinux/config file. Otherwise, the system may fail to start. If you must enable SELinux, see Enable or disable SELinux.
Check the remaining space on the system disk to ensure that it is not full.
Only VMs whose first disk is the system disk are supported. If the first disk is not the system disk, 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 ensure that the hostname, NTP source, and yum source can be configured. For more information, see Install cloud-init.
The logon password of the root account must be 8 to 30 characters in length and contain at least three of the following character types: uppercase letters, lowercase letters, digits, and special characters. Special characters can be
( ) ` ~ ! @ # $ % ^ & * - _ + = | { } [ ] : ; ' < > , . ? /.GRUB version requirement: For Linux operating systems, you must update GRand Unified Bootloader (GRUB) to version 1.99 or later.
Supported operating systems
CentOS 6, 7, 8
Ubuntu 10, 12, 14, 16, 17, 18, 19, 20
Debian 7, 8, 9, 10
SUSE 11, 12, 15
openSUSE 13, 42, 15
RHEL 5, 6, 7, 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 system disk partitions is not supported. Only a single root partition is supported.
Do not install qemu-ga in the system. Otherwise, some services required by ECS may become unavailable.
System disk partitions (root partitions) built across disks using Logical Volume Manager (LVM) are not supported. Otherwise, the ECS instance may fail to start.
VMware platform
Item
Description
vCenter version
vCenter 6.7 and later are supported. The migration gateway must be able to access the vCenter server and ESXi hosts that manage the backup VMs using their FQDNs or IP addresses.
Hardware version
The VM hardware version must be 10 (corresponding to ESXi 5.5) or later.
Data synchronization
Verification of sync results
After a sync task is complete, you must perform data consistency verification between the source and destination.
After a data synchronization task is complete, you must verify the data at the destination to ensure its accuracy. If you delete the source data without verifying the destination data, you are solely responsible for any data loss and its consequences.
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: Operating system versions supported by the backup client
The backup client does not support 32-bit operating systems or Windows Server versions earlier than 2008. Ensure that your system environment meets the requirements.
Linux operating systems
Limitations | Details |
Supported operating system versions |
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Unsupported operating system versions |
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Windows operating systems
Limitations | Details |
Supported operating system versions |
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Unsupported operating system versions |
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