All Products
Search

This Product

    Cloud Backup:Limits

    Document Center

    Cloud Backup:Limits

    Last Updated:Dec 05, 2024

    This topic describes the limits on the async replication feature of Cloud Backup.

    Limits on regions and zones

    The async replication feature is in public preview. More regions will be available in the future. The regions that you can select when you create a site pair shall prevail. The async replication feature is supported in the following regions and zones:

    • China (Hangzhou): Zone G, Zone H, Zone I, and Zone K

    • China (Shanghai): Zone B, Zone E, Zone F, Zone G, and Zone L

    • China (Beijing): Zone F, Zone G, Zone H, and Zone J

    • China (Zhangjiakou): Zone A

    • China (Shenzhen): Zone D and Zone E

    • China (Heyuan): Zone A and Zone B

    • China (Chengdu): Zone A and Zone B

    • China (Hong Kong): Zone B and Zone C

    • Singapore: Zone B and Zone C

    • Indonesia (Jakarta): Zone A and Zone B

    • US (Silicon Valley): Zone A and Zone B

    • US (Virginia): Zone A and Zone B

    • SAU (Riyadh - Partner Region): Zone A and Zone B

    • China East 2 Finance: Zone G and Zone K

    • China North 2 Finance (Private Preview): Zone L and Zone K

      Important

      Alibaba Finance Cloud and the Alibaba Cloud public cloud are isolated from each other. Async replication and disaster recovery cannot be performed between the two.

    Limits on specifications and ECS disks

    The following table describes the limits on specifications that apply to the async replication and replication pair-consistent group features.

    Item

    Description

    Number of replication pairs that can be created per disk

    1

    Number of replication pairs that can be added per replication pair-consistent group

    17

    Replication cycle

    15 minutes (Data is asynchronously replicated from a primary disk to a secondary disk every 15 minutes.)

    Replication rate

    The replication rate can be up to 100 MB/s and may vary based on the system load.

    Primary disk category

    Primary disks must be ESSDs or ESSD AutoPL disks.

    Secondary disk category

    Secondary disks must be of the same disk category and have the same performance level and capacity as the corresponding primary disks.

    The following table describes the limits on disks that apply to the async replication and replication pair-consistent group features.

    Note

    • ①: After a replication pair is activated, the secondary disk enters the read-only state and no users have write permissions on the disk.

    • ②: Due to the recovery point objective (RPO), the data of a snapshot created for a primary disk may be inconsistent with that of a snapshot created at the same time for the associated secondary disk.

    • ③: Replication is restricted to encrypted disks. Cross-replication between encrypted disks and unencrypted disks is not supported.

    Item

    Supported by the primary disk

    Supported by the secondary disk

    Read and write operations

    √

    ×①

    Disk deletion

    ×

    ×

    Disk initialization

    ×

    ×

    Disk resizing

    ×

    ×

    Disk attaching

    √

    ×

    Snapshot creation

    √

    ✓②

    Rollback based on snapshots

    √

    ×

    Disk category change

    ×

    ×

    Performance level change

    ×

    ×

    Disk encryption

    √

    ✓③

    Multi-attach

    ×

    ×

    Disk migration together with instances

    ×

    ×

    Limits on ECS networks

    The following limits apply to Elastic Compute Service (ECS) networks:

    • Single elastic network interface (ENI):

      After a failover, the ENI cannot be automatically configured for some operating systems at the disaster recovery site. After the failover, check and configure the ENI at the disaster recovery site to ensure that the network works properly. For more information, see Configure a secondary ENI.

    • Multiple ENIs:

      • After an ECS instance is bound to a secondary ENI, some images cannot automatically identify the IP address of the secondary ENI or add a route. As a result, the secondary ENI cannot work properly.

      • If an ECS instance is configured with a secondary ENI, check the IP address of the secondary ENI after a failover. This ensures that the secondary ENI works as expected. For more information, see Configure a secondary ENI.

    • Only ENIs and ECS instances that reside in the same virtual private clouds (VPCs) as the disaster recovery site pair are supported.

    Limits on configuration quotas

    • A single user can create a maximum of 1,000 disaster recovery site pairs.

    • A maximum of 512 protection groups can be configured for each disaster recovery site pair.

    • Each protection group supports a maximum disk capacity of 32 TB and a maximum of 17 disks.

    Limits on consistency guarantee

    The async replication feature supports only crash consistency and does not support application consistency. For applications and databases that have high requirements for consistency, we recommend that you configure direct writes of data to disks based on application and database documentation. This ensures data consistency and reduces the risk of extended recovery time due to asynchronous data writes when a disaster occurs.