limits of ECS Disaster Recovery-Cloud Backup(Cloud Backup)-阿里云帮助中心

ECS disaster recovery (CDR) has specific requirements and limits on operating systems, platforms, databases, and applications. Review these limits before setting up disaster recovery.

Operating systems

CDR supports only the following operating systems.

Important

Only the operating systems listed in the following table are supported. For unsupported operating systems, use the asynchronous replication feature instead.

Operating system	Supported versions and requirements
Windows Server	2008 R2, 2012, 2012 R2, and 2016
Linux	Important For Linux systems, the /boot partition and the / partition must reside on the same disk. If they do not, resize the disk manually before registering the protected instance for CDR. Red Hat Enterprise Linux 7.0 to 7.9 Red Hat Enterprise Linux 6.0 to 6.10 CentOS 7.0 to 7.9 CentOS 6.0 to 6.10 (64-bit only) SUSE Linux Enterprise Server 12.0 to 12.3 (64-bit only) Important SUSE Linux Enterprise Server 12.1 running on a VMware virtual machine (VM) may display a black screen after a restart. This is caused by operating system errors, not by CDR. Alibaba Cloud Linux 2.1903 LTS 64-bit The following kernel versions are supported: 4.19.91-25.1.al7.x86_64 4.19.91-24.1.al7.x86_64 4.19.91-23.al7.x86_64 4.19.91-22.2.al7.x86_64

Platforms

CDR uses disk-level data replication and is independent of the underlying platform. The following table lists tested and verified platforms.

Infrastructure	Version
Physical machine	Full support
vSphere	6.7 and later

Databases and applications

CDR's replication technology is application-agnostic and supports all databases and applications.

Most applications require automated scripts to maintain consistency during updates. Alibaba Cloud provides tools and scripts that work with CDR to help applications recover smoothly.

Other limits

CDR has the following additional limits:

ECS instances that use the NVMe protocol to communicate with disks do not support disaster recovery.
A protected ECS instance must have at least 1.5 GB of available memory reserved for the operating system. Otherwise, disaster recovery may fail.
Full restore is not supported for an ECS instance whose system disk resides on a physical volume larger than 2 TB.
A single physical volume of a data disk must not exceed 32 TB.
Disk write limits:
- Linux
  
  If the average I/O size is 4 KB, the maximum disk write speed is approximately 10 MB/s. If the average I/O size is 64 KB, the maximum disk write speed is approximately 30 MB/s.
- Windows
  
  The maximum disk write speed is 10 MB/s.
The maximum total throughput for a single site pair is 400 Mbps.

Exceeding this limit may increase both the Recovery Point Objective (RPO) and Recovery Time Objective (RTO). When designing a disaster recovery solution, evaluate the workload of protected servers and estimate the disk write throughput.