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    ApsaraDB for ClickHouse:Limits

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    ApsaraDB for ClickHouse:Limits

    Last Updated:Oct 13, 2025

    This topic describes usage limits.

    Cluster purchase and configuration limits

    Description

    Limit

    Maximum number of clusters per Alibaba Cloud account

    30

    Maximum number of node groups per cluster

    24

    Maximum number of database accounts per cluster

    500

    Total number of scale-out, scale-in, and upgrade/downgrade operations per cluster per day

    12

    Maximum number of databases per cluster

    256

    Specification limits

    ApsaraDB for ClickHouse

    Resource name

    Memory usage of the underlying operating system

    Memory usage of related management services

    Compute node

    About 800 MB to 13 GB. Larger specifications consume more memory.

    About 500 MB.

    ZooKeeper

    About 800 MB to 2.5 GB. Larger specifications consume more memory.

    About 500 MB.

    Feature limits

    • High-availability clusters must use replicated table engines.

    • By default, all servers automatically form a cluster named default. Use the ON CLUSTER default clause to execute Data Definition Language (DDL) statements on all servers.

    • Configuring remote_servers is not supported.

    • The File and URL table engines are not supported.

    • The File and URL table functions are not supported.

    • Custom user Profiles are not supported.

    Object naming convention limits

    Object

    Naming rule

    Limit

    Database name

    Must start with a lowercase letter. Can contain letters, digits, and underscores (_). Cannot contain two or more consecutive underscores. The length cannot exceed 64 characters.

    The database name cannot be `system`. The name `system` is reserved for a built-in database.

    Table name

    Must start with a letter or an underscore (_). Can contain letters, digits, and underscores (_). The length must be 1 to 127 characters.

    The name cannot contain quotation marks, exclamation points (!), or spaces. The name cannot be a SQL reserved keyword.

    Column name

    Must start with a letter or an underscore (_). Can contain letters, digits, and underscores (_). The length must be 1 to 127 characters.

    The name cannot contain quotation marks, exclamation points (!), or spaces. The name cannot be a SQL reserved keyword.

    Account name

    Must start with a lowercase letter and end with a lowercase letter or a digit. Can contain lowercase letters, digits, and underscores (_). The length must be 2 to 16 characters.

    -

    Password requirements

    Must be 8 to 32 characters long and contain at least three of the following character types: uppercase letters, lowercase letters, digits, and special characters. Special characters include `!`, `@`, `#`, `$`, `%`, `^`, `&`, `*`, `()`, `_`, `+`, `-`, and `=`.

    -

    Bandwidth limits

    Community-Compatible Edition

    Cluster bandwidth is determined by the bandwidth limits of the ECS specifications and disk performance.

    Enterprise Edition

    • Disk storage:

      Type

      ESSD_L1

      ESSD_L2

      Cluster read/write bandwidth (MB/s)

      min{120 × Number of nodes + 0.5 × Total purchased storage, 460 × Number of nodes}

      min{120 × Number of nodes + 0.5 × Total purchased storage, 980 × Number of nodes}

    • OSS storage:

      Region

      Cluster read/write bandwidth (Gb/s)

      Per-node limit

      Compute Unit (CCU)

      Read bandwidth (Gb/s)

      Write bandwidth (Gb/s)

      QPS

      • China (Beijing)

      • China (Shanghai)

      • China (Hangzhou)

      • China (Shenzhen)

      • Read: 100

      • Write: 20

      [4,8)

      1.6

      0.6

      • Read: (Maximum CCUs per node × 4) × 25

      • Write: (Maximum CCUs per node × 4) × 2

      • Burst read: (Maximum CCUs per node × 4) × 25 × 300

      • Burst write: (Maximum CCUs per node × 4) × 2 × 300

      Note

      • Maximum CCUs per node = Upper limit of the elastic CCU range / Number of nodes.

        If the upper CCU limit is less than 64, the number of nodes is 2. If the upper CCU limit is greater than 64, the number of nodes = Upper CCU limit / 32.

      • Maximum memory per node (GB) = Maximum CCUs per node × 4.

      For example, if the elastic CCU range is [4, 8), the maximum CCUs per node is 8 / 2 = 4, and the maximum memory per node is 4 × 4 = 16 GB.

      [8,16)

      2.5

      0.8

      [16,32)

      4.1

      1

      [32,48)

      8.3

      1.7

      [48,64)

      10.8

      2.2

      [64,64]

      13.3

      2.9

      China (Ulanqab)

      • Read: 10

      • Write: 10

      [4,8)

      1

      1

      [8,16)

      1.3

      1.3

      [16,32)

      1.6

      1.6

      [32,48)

      2

      2

      [48,64)

      2.6

      2.6

      [64,64]

      3.4

      3.4

      Singapore

      • Read: 100

      • Write: 5

      [4,8)

      1.6

      0.5

      [8,16)

      2.5

      0.65

      [16,32)

      4.1

      0.8

      [32,48)

      8.3

      1

      [48,64)

      10.8

      1.3

      [64,64]

      13.3

      1.7

      • China (Hong Kong)

      • Japan (Tokyo)

      • US (Virginia)

      • Germany (Frankfurt)

      • Read: 5

      • Write: 5

      [4,8)

      2

      0.5

      [8,16)

      3

      0.65

      [16,32)

      5

      0.8

      [32,48)

      10

      1

      [48,64)

      13

      1.3

      [64,64]

      16

      1.7

    Note

    For the bandwidth limits of Enterprise Edition clusters in other regions, refer to the limits for the China (Hong Kong) region.

    Comparison of read/write latency across storage classes

    Storage class

    Domain name type

    Accelerator

    4 KiB read response time (RT) (ms)

    4 KiB write RT (ms)

    OSS locally redundant storage

    Standard domain name

    No

    Fluctuates between 13.8 and 14.2

    Fluctuates between 24.7 and 26.4

    Disk type

    N/A

    N/A

    1.2

    2.6