Shulou(Shulou.com)06/01 Report--

Part of this article is excerpted from the product introduction of distributed database middleware (DDM) service of Huawei Cloud help Center.

Background

With the growth of business, the storage space of logical library is insufficient, and the pressure of concurrency is great.

Solution

At this point, the logical database of DDM instances can be smoothly expanded, and the data storage capacity and concurrency support capacity can be improved by adding RDS instances. Without interrupting the application service, the database storage space is expanded by adding RDS instances. Capacity expansion can not only solve the bottleneck of data storage capacity, but also indirectly improve database performance by increasing concurrent computing power. The capacity expansion can be completed through the operation of the DDM management console, the application does not need to be modified, and the progress of capacity expansion supports visual tracking.

Smooth expansion

Smooth expansion is a horizontal expansion method, which increases the overall data storage capacity by increasing the number of RDS instances, and smoothly expands the sub-database to the newly added RDS instances to ensure that all data is evenly distributed on each sub-database, thus reducing the processing pressure on a single RDS instance.

The principle of smooth expansion is shown in the following figure.

Practice of smooth expansion of logical Library

Operation scene

The expansion of logical library involves data migration. The details are as follows:

1. A copy of all global tables will be copied and stored in the corresponding shard of the new RDS instance.

2. The sharded table data will be redistributed and stored.

3. Single table is stored on the default shard, and there is no need to migrate single table data in the process of capacity expansion.

Note: when the RDS storage space is insufficient, it is recommended to expand the disk capacity of a RDS instance under the logic library to expand the RDS instance storage space. When the concurrency pressure is too high to meet the business requirements, it is recommended to add RDS instances to smooth capacity expansion by following the following operations. When the logical table with "split algorithm" is "Range", only physical tables are created on the new shards without data migration. After the expansion is successful, users need to manually modify the sharding rules in the "Range" table and add new sharding rules.

Operation steps

1. Log in to the management console.

2. Select "Database > distributed Database Middleware" on the navigation to enter the overview page.

Click "DDM instance Management" in the left menu bar to enter the "DDM instance Management" page.

3. Click the DDM instance name to enter the basic information page of the instance.

4. On the instance basic information page, select the "Logic Library Management" tab to view the DDM instance logic library.

5. Click "smooth expansion" in the right operation bar of the logical library that needs to be expanded.

6. Check the RDS instance to be expanded on the left side of the "smooth expansion" pop-up box, and click "OK". You can check the progress of capacity expansion on the "logical Library Management" page. The expansion process takes about 5-30 minutes, depending on the actual amount of data to be migrated. When the "logical library status" is "running", the expansion is successful, and the "used RDS" column will present the newly expanded RDS instance.

Description: smooth expansion can only be carried out when the logical library status is "running". In a DDM instance, only one instance logic base can be smoothly expanded at the same time, while in different DDM instances, the instance logic base can be expanded at the same time.

Note: the restrictions on smooth expansion are as follows:

1. RDS instances and DDM instances need to be in the same VPC, and RDS instances are not used by other DDM instances.

2. There must be a table under the logic library to expand the capacity smoothly.

3. You cannot expand the capacity of an instance when there is a node failure.

4. In a DDM instance, only one instance logic base can be smoothly expanded at the same time; in different DDM instances, the instance logic base can be expanded at the same time.

5. You are not allowed to use RDS instances that are being expanded to build databases and tables.

6. Only 50 RDS instances can be expanded at most.

7. The maximum capacity expansion specification is no more than 20 tables for each shard. Each table does not exceed 8 million data.

The above is the practical solution for the smooth expansion of the database in a second. For more information, please click DDM, the distributed database middleware.

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