SDRS Usage Restrictions

Before using SDRS, learn about the constraints listed in the following tables.

**Table 1** Asynchronous replication constraints
Constraint	Description
Architecture	Constraints on architecture types and versions: For Huawei Cloud Stack, the version must be 6.5 or later. For Huawei Cloud Stack Online, all versions are supported.
Specifications	Constraints on specifications: Memory on each cloud disaster recovery gateway, production site server, and disaster recovery site server must be greater than 2 GB. One disaster recovery gateway can protect a maximum of 20 protected instances.
Server	Constraints on servers: Only KVM servers can be used for disaster recovery.
Function	Constraints on functions: Shared EVS disks are not supported. Failback is not supported if the production site servers are billed on a yearly/monthly basis. Bare Metal Servers (BMSs) are not supported. EVS disk creation, deletion, and capacity expansion are not allowed on protected instances. The system disk of a disaster recovery gateway server cannot use LVM.

**Table 2** Synchronous replication constraints
Constraint	Description
Compute	Constraints on server types: Kunpeng ECSs are not supported. x86-based, GPU-accelerated and FPGA-accelerated ECSs are not supported.
Replication	Constraints on servers: The servers must be from two AZs of the same region. BMSs are not supported. The following types of servers cannot be used to create protected instances: Large Memory (Xen): This type of servers is bound to InfiniBand NICs. Disk Intensive I (Xen): This type of servers has local disks. Disk Intensive II (KVM): This type of servers has local disks.
Replication	Constraints on EVS disks: Disks used to create replication pairs cannot be deleted, and the disk snapshot cannot be used to roll back data.
Storage	Only servers using EVS or DSS disks are supported.
Application	Storage-based synchronous replication ensures disk data consistency but does not guarantee application data consistency. If your applications support crash consistency, you can run and replicate applications.
Deployment model	VPC migration: Servers at the production site and those at the disaster recovery site are in the same VPC. NIC migration and multiple NICs are supported for each server.
Service interconnection	Tag Management Service (TMS) is supported only via API.
Backup and restore	Only servers at the production site can be backed up and restored. Servers at the disaster recovery site can only be backed up.