This topic describes the limits on PolarDB for MySQL.

Edition Node instance type

CPU and memory specification

Memory for file system Maximum files Maximum connections
Cluster (Dedicated)

2 cores and 8 GB of memory

800 MB 1,024,000 6,000

4 cores and 16 GB of memory

1,300 MB 2,048,000 8,000

8 cores and 32 GB of memory

2,400 MB 4,096,000 10,000

8 cores and 64 GB of memory

3,500 MB 6,144,000 16,000

16 cores and 128 GB of memory

10,240 MB 20,480,000 32,000

32 cores and 256 GB of memory

10,240 MB 20,480,000 64,000

64 cores and 512 GB of memory

10,240 MB 20,480,000 64,000

88 cores and 710 GB of memory

10,240 MB 20,480,000 100,000
Cluster (General-purpose)

2 cores and 4 GB of memory

800 MB 1,024,000 1,800

2 cores and 8 GB of memory

800 MB 1,024,000 2,000

4 cores and 8 GB of memory

1,300 MB 2,048,000 3,000

4 cores and 16 GB of memory

1,300 MB 2,048,000 6,000

8 cores and 16 GB of memory

1,300 MB 2,048,000 6,000

8 cores and 32 GB of memory

2,400 MB 4,096,000 10,000

16 cores and 64 GB of memory

3,500 MB 6,144,000 16,000

32 cores and 128 GB of memory

10,240 MB 20,480,000 32,000
Single Node

4 cores and 8 GB of memory

800 MB 1,024,000 6,000
Archive Database (High Compression Ratio)

4 cores and 16 GB of memory

5,500 MB 10,240,000 8,000

8 cores and 32 GB of memory

10,240 MB 20,480,000 10,000

8 cores and 64 GB of memory

10,240 MB 20,480,000 16,000

16 cores and 128 GB of memory

10,240 MB 20,480,000 32,000

32 cores and 256 GB of memory

10,240 MB 20,480,000 64,000

64 cores and 512 GB of memory

10,240 MB 20,480,000 64,000

88 cores and 710 GB of memory

10,240 MB 20,480,000 100,000
Archive Database Cluster Edition (Dedicated)

4 cores and 16 GB of memory

1,300 MB 2,048,000 8,000

8 cores and 32 GB of memory

2,400 MB 4,096,000 10,000

8 cores and 64 GB of memory

3,500 MB 6,144,000 16,000

16 cores and 128 GB of memory

10,240 MB 20,480,000 16,000

32 cores and 256 GB of memory

10,240 MB 20,480,000 64,000

64 cores and 512 GB of memory

10,240 MB 20,480,000 64,000

88 cores and 710 GB of memory

10,240 MB 20,480,000 100,000
Archive Database Cluster Edition (General-purpose)

4 cores and 8 GB of memory

1,300 MB 2,048,000 3,000

4 cores and 16 GB of memory

1,300 MB 2,048,000 6,000

8 cores and 16 GB of memory

1,300 MB 2,048,000 6,000

8 cores and 32 GB of memory

2,400 MB 4,096,000 10,000

16 cores and 64 GB of memory

3,500 MB 6,144,000 16,000

32 cores and 128 GB of memory

7,000 MB 12,288,000 32,000

Parameters in the preceding table:

  • 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 files
    User files, about 100 database system files, and log files are included. To view the number of log files, run the SHOW POLAR LOGS command. A PolarDB table occupies two files. A partition table occupies N + 2 files, 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 tables

    In this case, you must delete some tables or upgrade the specifications of your cluster.

  • Maximum 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.

Table 1. Other limits
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 Not supported.

FAQ

  • Compared with native MySQL, what is the maximum size of data that a single table can store in PolarDB?

    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 number of read-only nodes does not depend on the maximum number of connections. 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.