This topic describes the limits of PolarDB for MySQL.
| Edition | Node instance type
CPU and memory specification |
Memory for file system | Maximum number of files | Maximum number of connections |
|---|---|---|---|---|
| Cluster Edition (Dedicated) | polar.mysql.x4.medium
2 cores, 8 GB memory |
800 MB | 1,024,000 | 6,000 |
| polar.mysql.x4.large
4 cores,16 GB memory |
1,300 MB | 2,048,000 | 8,000 | |
| polar.mysql.x4.xlarge
8 cores, 32 GB memory |
2,400 MB | 4,096,000 | 10,000 | |
| polar.mysql.x8.xlarge
8 cores, 64 GB memory |
3,500 MB | 6,144,000 | 16,000 | |
| polar.mysql.x8.2xlarge
16 cores, 128 GB memory |
10,240 MB | 20,480,000 | 32,000 | |
| polar.mysql.x8.4xlarge
32 cores, 256 GB memory |
10,240 MB | 20,480,000 | 64,000 | |
| polar.mysql.x8.8xlarge
64 cores, 512 GB memory |
10,240 MB | 20,480,000 | 64,000 | |
| polar.mysql.x8.12xlarge
88 cores, 710 GB memory |
10,240 MB | 20,480,000 | 100,000 | |
| Cluster Edition (General-purpose) | polar.mysql.g2.medium
2 cores, 4 GB memory |
800 MB | 1,024,000 | 1,800 |
| polar.mysql.g4.medium
2 cores, 8 GB memory |
800 MB | 1,024,000 | 2,000 | |
| polar.mysql.g2.large
4 cores, 8 GB memory |
1,300 MB | 2,048,000 | 3,000 | |
| polar.mysql.g4.large
4 cores,16 GB memory |
1,300 MB | 2,048,000 | 6,000 | |
| polar.mysql.g2.xlarge
8 cores, 16 GB memory |
1,300 MB | 2,048,000 | 6,000 | |
| polar.mysql.g4.xlarge
8 cores, 32 GB memory |
2,400 MB | 4,096,000 | 10,000 | |
| polar.mysql.g4.2xlarge
16 cores, 64 GB memory |
3,500 MB | 6,144,000 | 16,000 | |
| polar.mysql.g4.4xlarge
32 cores, 128 GB memory |
10,240 MB | 20,480,000 | 32,000 | |
| Single Node Edition | polar.mysql.s2.large
4 cores, 8 GB memory |
800 MB | 1,024,000 | 6,000 |
| X-Engine Edition (Dedicated) | polar.mysql.ax4.large
4 cores,16 GB memory |
1,300 MB | 2,048,000 | 8,000 |
| polar.mysql.ax4.xlarge
8 cores, 32 GB memory |
2,400 MB | 4,096,000 | 10,000 | |
| polar.mysql.ax8.xlarge
8 cores, 64 GB memory |
3,500 MB | 6,144,000 | 16,000 | |
| polar.mysql.ax8.2xlarge
16 cores, 128 GB memory |
10,240 MB | 20,480,000 | 32,000 | |
| polar.mysql.ax8.4xlarge
32 cores, 256 GB memory |
10,240 MB | 20,480,000 | 64,000 | |
| polar.mysql.ax8.8xlarge
64 cores, 512 GB memory |
10,240 MB | 20,480,000 | 64,000 | |
| polar.mysql.ax8.12xlarge
88 cores, 710 GB memory |
10,240 MB | 20,480,000 | 100,000 | |
| X-Engine Edition (General-purpose) | polar.mysql.ag2.large
4 cores, 8 GB memory |
1,300 MB | 2,048,000 | 3,000 |
| polar.mysql.ag4.large
4 cores,16 GB memory |
1,300 MB | 2,048,000 | 6,000 | |
| polar.mysql.ag2.xlarge
8 cores, 16 GB memory |
1,300 MB | 2,048,000 | 6,000 | |
| polar.mysql.ag4.xlarge
8 cores, 32 GB memory |
2,400 MB | 4,096,000 | 10,000 | |
| polar.mysql.ag4.2xlarge
16 cores, 64 GB memory |
3,500 MB | 6,144,000 | 16,000 | |
| polar.mysql.ag4.4xlarge
32 cores, 128 GB memory |
7,000 MB | 12,288,000 | 32,000 |
The preceding table describes the limits of PolarDB for MySQL on the following metrics:
- Memory for file system
The amount of memory that is consumed by the file system when the upper limit of the storage for a cluster is reached. In this case, the cluster handles normal read and write requests (without performance stress testing and DDL operations on large tables). If the upper limit of the storage is not reached, the consumed amount of memory is less than the specified value of this parameter.
- Maximum number of files
User files, about 100 database system files, and log files are included. To view the number of log files, run the
SHOW POLAR LOGScommand. A PolarDB table occupies two files. A partitioned table occupiesN + 2files, where N indicates the number of partitions. The following error message appears when you create a table after the maximum number of files is reached:ERROR 3017 (HY000): Too many files. PolarDB only supports 2048 files every 10GB disk size. Please drop some tables/databases before creating new tablesIn this case, you must delete some tables or upgrade the specifications of your cluster.
- Maximum number of connections
In the preceding table, the number of connections refers to the number of connections for an individual node. It does not refer to the total number of connections in a cluster.
| Item | Limit |
|---|---|
| Table name | The name of a table in a cluster of any specification can be up to 64 letters and digits or 50 Chinese characters in length. |
| Serializable isolation level | Serializable isolation is not supported. |
FAQ
- What is the maximum size of data that a single table can store in PolarDB compared with native MySQL?
The size of a single table is unlimited in PolarDB. However, the size of a table depends on the size of the disk space.
- Can I create 10,000 databases in PolarDB? What is the maximum number of databases?
Yes, you can create 10,000 databases in PolarDB. The maximum number of tables for a PolarDB cluster depends on the number of files.
- Does the maximum number of connections depend on the number of read-only nodes? Can
I increase the maximum number of connections by adding read-only nodes?
No, the maximum number of connections does not depend on the number of read-only nodes. The maximum number of connections for PolarDB depends on the node specifications. To increase the maximum number of connections, you can upgrade the cluster specifications. For more information, see Manually upgrade or downgrade a PolarDB cluster.