Constraints

General

• A vault can be associated with only one backup policy.
• A vault can be associated with only one replication policy.
• A vault can be associated with a maximum of 256 resources.
• A maximum of 32 backup policies and 32 replication policies can be created.
• Only backups in the Available or Locked vaults can be used to restore data.
• Backups in a Deleting vault cannot be deleted.
• Backups cannot be downloaded to a local PC or uploaded to OBS.
• A vault and its associated servers or disks must be in the same region.
• Concurrent data restoration is not supported.
• Auto capacity expansion does not take effect if it is enabled after the vault is full.
• If a backup of a resource is in progress, other policy or manual backups of this resource will not be performed.

Cloud Disk Backup

• Only disks in the Available or In-use state can be backed up.
• Frozen disks in the retention period cannot be backed up.
• A new disk must be at least as large as the backup's source disk.
• Cloud disk backups cannot be replicated to other regions.
• Backup and restoration of local disks are not supported.

Cloud Server Backup

• A maximum of 10 shared disks can be backed up with a cloud server.
• Only backups in the Available or Locked vaults can be used to create images and be replicated to different regions.
• Frozen servers in the retention period cannot be backed up.
• Cloud servers support crash-consistent backup, whereas database servers support application-consistent backup in addition to crash-consistent backup.
• You can back up specific disks on a server, but such a backup must be restored as a whole. File- or directory-level restoration is not supported.
• Images cannot be created from backups if the amount of resources associated with a server backup vault exceeds the quota.
• You are advised not to back up a server whose disk size exceeds 4 TB.
• Backups can be replicated only to regions that have replication capabilities.
  • A backup can be replicated only when it meets all of the following conditions:
    1. It is an ECS backup.
    2. It contains system disk data.
    3. It is in the Available state.
  • Only backups can be replicated. Backup replicas cannot be replicated again but can be used to create images.
  • A backup can be replicated to multiple regions but can have only one replica in each destination region. Manual replication: A backup can be manually replicated to the destination region as long as it has no replica in that region. A backup can be manually replicated again if its replica in the destination region has been deleted.
  • Only replication-supported regions can be selected as destination regions.

SFS Turbo Backup

• Only file systems in the Available state can be backed up.
• An SFS Turbo file system backup cannot be used to restore data to the original file system.
• Backups can be replicated only to regions that have replication capabilities.
  • A backup can be replicated only when it meets all of the following conditions:
    1. It is generated for an SFS Turbo file system.
    2. It is in the Available state.
  • Only backups can be replicated. Backup replicas cannot be replicated again but can be used to create SFS Turbo file systems.
  • A backup can be replicated to multiple regions but can have only one replica in each destination region. Manual replication: A backup can be manually replicated to the destination region as long as it has no replica in that region. A backup can be manually replicated again if its replica in the destination region has been deleted.
  • Only replication-supported regions can be selected as destination regions.

Hybrid Cloud Backup - VMware Backup

• VM backups from the following VMware vSphere versions can be synchronized to the cloud: 5.1, 5.5, 6.0, 6.5, 6.7.
• Currently, only VMware ESXi VMs can be backed up to the cloud.
• To achieve better performance and operation experience, only the OSs listed in Table 1 allows for cloud recovery. These OSs have passed the the compatibility test. If you only need to restore data to on-premises VMware VMs, there is no restriction on the OS version.
• The VDDK version of VMware 6.7 or earlier VMs must be 6.0.3.
• Backups synchronized to the cloud cannot be used to create cloud servers.
• Backups synchronized to the cloud can only be restored to existing cloud servers running the same type of OS. Recovery of partial disks on a VM is not supported.
• Servers whose system disks are configured with LVM cannot be restored on cloud.
• Before the restoration, configure security groups according to the procedure. Otherwise, the restoration may fail.
• The backup bandwidth should be at least 100 Mbit/s. The sizes of disks on the VMware VMs to be backed up to the cloud should be integers in GB.
• When recovering data on the cloud from a Windows VMware backup, the system disk's boot partition number of the backup must be 2.

  Table 1 OSs that support restoration to the cloud

  OS	Supported Version
  Windows	Windows 7 Windows Server 2008 R2 Windows Server 2012 Windows Server 2012 R2 Windows Server 2016 Windows Server 2019
  CentOS	CentOS 6.4 CentOS 6.5 CentOS 7.2 CentOS 7.3 CentOS 7.4 CentOS 7.5 CentOS 7.6 CentOS 7.7
  Red Hat	Red Hat 6.4 Red Hat 6.5 Red Hat 7.2

Desktop Backup

• Only desktops in the Available or In-use state can be backed up.

File Backup

• Before backing up a file, ensure that the file is not being used or changed by an application, and the backup client has the read permissions on this file. Otherwise, the backed-up data will be incomplete.
• Before backing up a file, ensure that the file is not being used or changed by a process, and the backup client has the read permissions on this file. Otherwise, the backed-up data will be incomplete.
• You are advised not to restore file backups when applications are running. Stop the applications and then restore files.
• One backup client can have a maximum of 8 files and directories added.
• Each resource can only have one Agent installed.
• The number of resources where the Agent can be installed is not limited.
• A single directory can contain a maximum of 500,000 files, and you are advised to reserve at least 4 GB of memory on each backup client to perform file backups.
• One path can contain a maximum of 200 characters.
• The maximum bandwidth allowed for file backup data transmission is 16 Gbit/s. If the maximum bandwidth is reached, flow control will be triggered.
• File backup cannot back up the files stored in SFS file systems that are mounted to cloud servers.
• Backup may fail on directories with frequent file writes in Windows.
• At least 50 Mbit/s network bandwidth is required in cross-cloud or cross-region scenarios.

Application-Consistent Backup