DDM Practice: Database second-level smoothing scaling scheme

This part of this article is an excerpt from the Distributed Database Middleware (DDM) service of Huawei Cloud Help Center.

Background

With the growth of the business, the storage space of the logical library is not enough and the concurrency pressure is large.

Solution Solutions

In this case, the DDM instance logical library can be scaled up smoothly, increasing the RDS instance to improve the data storage capability and concurrency support capability. Extend the database storage space with new RDS instances without disrupting application services. In addition to solving the bottleneck of data storage capacity, expansion can indirectly improve database performance by increasing concurrent computing capacity. With the DDM Management console, the capacity is expanded, the application does not need to be modified, and the expansion progress supports visual tracking.

Smooth expansion

Smooth expansion is a way of horizontal expansion, by increasing the number of RDS instances to increase the overall data storage capacity, the sub-database is smoothly expanded to the new RDS instance, to ensure that all data are evenly distributed on each sub-library, reducing the processing pressure of a single RDS instance.

The principle of smooth scaling is as shown.

The practice of smooth expansion of logical library

Operating Scenarios

Logical library expansion involves data migration. The following conditions are specific:

1. All global tables will be copied and stored in the corresponding shards of the new RDS instance.

2, the Shard table data will be redistributed and stored.

3, the single table is stored on the default Shard, the expansion process does not need to migrate single-table data.

Note: When you are running out of RDS storage space, it is recommended that you expand the RDS instance storage space by disk expansion for an RDS instance under the logical library. When the concurrency pressure is not enough to meet the business requirements, it is recommended to increase the RDS instance to smooth expansion as follows. When the logical table for "Range" of the split algorithm is expanded smoothly, only the physical table is created on the new Shard, not the data migration. After the expansion succeeds, the user needs to manually modify the "Range" table's shard rules, adding the new shard rules.

Operation Steps

1, login to the management console.
2. Select "Database > Distributed Database Middleware" on the navigation to go to the overview page.
Click "DDM Instance Management" on the left menu bar to go to the DDM Instance management page.
3. Click the DDM instance name to enter the instance basic information page.
4. On the Instance Basic Information page, select the "Logical Library Management" tab to view the DDM instance logical library.
5. Click "Smooth Expansion" on the right side of the logical library that needs to be expanded.
6. On the left side of the "smooth expansion" pop-up box, tick the RDS instance that needs to be expanded, and click OK. You can view the progress of the expansion on the "Logical Library Management" page, which takes approximately 5-30 minutes to scale, and is related to the amount of data actually needed to be migrated. When the logical library status is running, the expansion is successful and the RDS used column will present the newly expanded RDS instance.


Description: Only the logical library status is "running" for smooth scaling. In an DDM instance, only one instance logical library is allowed to be scaled smoothly, and the instance logical library can be expanded at the same time in different DDM instances.

Note: The following restrictions apply to smooth expansion:

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

2, the logical library must have a table in order to smooth the expansion.

3. If there is a node failure in the instance, the capacity cannot be expanded.

4. In an DDM instance, only one instance logical library is allowed to be scaled smoothly, and the instance logic library can be expanded at the same time in different DDM instances.

5, do not allow the use of RDS instances in the expansion of the database building table operations.

6, up to 50 RDS instances are supported.

7. The maximum size of the expansion is: no more than 20 sheets per shard. No more than 8 million data per table.

The above is about the database of second-level smooth expansion of the practice, want to learn more, welcome to open Distributed Database Middleware DDM view.

DDM Practice: Database second-level smoothing scaling scheme