The Replication Time Control (RTC) feature provided by Object Storage Service (OSS) can meet your compliance requirements or business requirements for cross-region replication (CRR). After the RTC feature is enabled, OSS replicates most of the objects that you uploaded to OSS within a few seconds and replicates 99.99% of objects within 10 minutes. In addition, the RTC feature provides near real-time monitoring of data replication. After you enable the RTC feature, you can view various metrics of replication tasks.

Billing rules

  • After you enable the RTC feature, you are charged for data replication traffic that is generated for RTC-enabled data replication tasks. For more information, see RTC traffic fees.
  • For a source region and a destination region that you configured for a replication task, you may claim a Service Credit if the replication bandwidth limit and queries per second (QPS) limit are not reached, and the service-level agreement (SLA) is not met in the billing month. For more information, see Alibaba Cloud International Website Object Storage Service Service Level Agreement.

Limits

  • Limits on regions
    • Regions in the Chinese mainland

      RTC is available in the following regions: China (Hangzhou), China (Shanghai), China (Qingdao), China (Beijing), China (Zhangjiakou), and China (Shenzhen).

    • Regions outside the Chinese mainland

      RTC is available in the following regions: US (Silicon Valley) and US (Virginia).

  • Limits on bandwidth
    • Bandwidth limits between two regions

      The bandwidth limit between two regions in the Chinese mainland is 10 Gbit/s. The bandwidth limit between two regions outside the Chinese mainland is 2 Gbit/s.

    • Bandwidth limits for a region

      The bandwidth limit for a region in the Chinese mainland is 20 Gbit/s. The bandwidth limit for a region outside the Chinese mainland is 4 Gbit/s.

    If your business requires higher bandwidth, contact technical support.

  • Limits on QPS
    • QPS limit for replication between two regions

      The QPS limit between two regions in the Chinese mainland is 10,000. The QPS limit between two regions outside the Chinese mainland is 5,000.

    • QPS limit for replication for a region

      The QPS limit for a region in the Chinese mainland is 20,000. The QPS limit for a region outside the Chinese mainland is 10,000.

    Important The preceding limits on QPS are for replication during non-sequential writes. The limit on QPS for replication during sequential writes is 2,000. If QPS is too large, the latency increases. We recommend that you do not upload a large number of objects whose names contain sequential prefixes. For more information about how to change sequential prefixes to random prefixes, see OSS performance and scalability best practices.

Enable the RTC feature

You can enable the RTC feature for new or existing CRR tasks. You can enable the RTC feature for CRR tasks to replicate all objects in a bucket, or to replicate objects with specified tags or whose names contain specified prefixes in a bucket.

Method 1: Enable the RTC feature when you create a CRR task

For more information, see CRR.

Method 2: Enable the RTC feature for an existing CRR task

  1. Log on to the OSS console.
  2. In the left-side navigation pane, click Buckets. On the Buckets page that appears, click the name of the bucket for which you want to enable the RTC feature.
  3. In the left-side navigation tree, choose Data Management > Cross-Region Replication.
  4. On the Cross-Region Replication tab, turn on Replication Time Control (RTC). In the message that appears, click OK.
Important If the RTC feature is enabled for a CRR task in which the Replicate Historical Data parameter is set to No, the RTC feature takes effect approximately 15 minutes after the feature is enabled. If the RTC feature is enabled for a CRR task in which the Replicate Historical Data parameter is set to Yes, the RTC feature takes effect after the historical data is replicated.

Monitor RTC metrics

After the RTC feature is enabled, you can click RTC Metric Monitoring on the Cross-Region Replication tab in the OSS console to view RTC metrics. For example, you can view the data replication latency, the amount of data to be replicated, and the number of operations to be replicated.

monitor

The following table describes the RTC metrics.

Metric Description
RTC Replication Latency The maximum data replication latency of a replication task or the recovery point objective (RPO) of a replication task.

For example, if the data replication latency is 1 minute, RTC ensures that all data written to the source bucket 1 minute ago is replicated to the destination bucket. When a disaster or an emergency occurs, you can restore the data to a point in time 1 minute ago.

RTC Amount of Data to Replicate The total size of data that you want to replicate to the destination bucket at a specific point in time for a replication task.

For example, 800 MB of data is written to the source bucket at 08:00, and the CRR feature replicates 600 MB of data between 08:00 and 08:01. At 08:01, the amount of data to be replicated is 200 MB.

RTC Number of Operations to Replicate The total number of operations that you want to replicate to the destination bucket at a specific point in time for a replication task.

Example:

  • 111 operations are performed on the source bucket at 08:00

    100 write operations + 10 delete operations + 1 operation to modify an object access control list (ACL)

  • The CRR feature replicates 101 operations between 08:00 and 08:01

    90 write operations + 10 delete operations + 1 operation to modify the object ACL

At 08:01, the number of operations to be replicated is 10.

RTC Write Bandwidth The write bandwidth of the data that you want to replicate from the source bucket for a replication task.
For example, the objects whose names contain the prefix1 and prefix2 prefixes are written to the source bucket at 08:00. The bandwidth is 800 Mbit/s.
  • The write bandwidth of the objects whose names contain the prefix1 prefix is 200 Mbit/s.
  • The write bandwidth of the objects whose names contain the prefix2 prefix is 600 Mbit/s.

If the replication task specifies that only the objects whose names contain the prefix1 prefix in the source bucket are replicated, the RTC write bandwidth is 200 Mbit/s.

RTC Write QPS The QPS of write, modify, and delete operations that you want to replicate from the source bucket for a replication task.
For example, the write, modify, and delete operations are performed on the source bucket at 08:00. The following items describe the QPS that corresponds to each operation:
  • The QPS for object upload is 10.
  • The QPS for object ACL modification is 5.
  • The QPS for object deletion is 3.

If the replication task specifies that only the write and modify operations performed on the source bucket are replicated, the RTC write QPS is 15.

If the replication task specifies that all operations performed on the source bucket are replicated, the RTC write QPS is 18.

Note The following items describe the RTC write operations:
  • Upload objects, modify object ACLs, and delete objects

    The following API operations are called to perform the preceding RTC write operations: PutObject, PostObject, AppendObject, CopyObject, DeleteObject, DeleteMultipleObjects, and PutObjectACL.

  • Initiate multipart upload tasks, upload parts, and replicate parts

    The following API operations are called to perform the preceding RTC write operations: InitiateMultipartUpload, UploadPart, UploadPartCopy, and CompleteMultipartUpload.

  • Add tags to and remove tags from objects

    The following API operations are called to perform the preceding RTC write operations: PutObjectTagging and DeleteObjectTagging.

  • Create a symbolic link

    The following API operation is called to perform the preceding RTC write operation: PutSymlink.