This topic describes the limitations of Alibaba Cloud ClickHouse.
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 resize operations per cluster per day | 12 |
Maximum number of databases per cluster | 256 |
Specification limits
Alibaba Cloud ClickHouse
Resource name | OS memory usage | Management service memory |
compute node | Approximately 800 MB to 13 GB. Memory usage scales with the specification. | Approximately 500 MB. |
ZooKeeper | Approximately 800 MB to 2.5 GB. Memory usage scales with the specification. | Approximately 500 MB. |
Feature limitations
A high-availability cluster must use a replicated table engine.
All servers automatically form a
defaultcluster. To execute DDL statements on all servers, you must use theON CLUSTER defaultclause.You cannot manually configure remote_servers.
The File and URL table engines are not supported.
The File and URL table functions are not supported.
You cannot customize profiles.
Object naming limits
Object | Naming rules | Limit |
Database | Must be up to 64 characters long, start with a lowercase letter, and contain only letters, numbers, and underscores (_). Consecutive underscores are not allowed. | The name cannot be |
Table | Must be 1 to 127 characters long, start with a letter or an underscore (_), and contain only letters, numbers, and underscores. | The name cannot contain quotation marks ('), exclamation points (!), spaces, or SQL reserved keywords. |
Column | Must be 1 to 127 characters long, start with a letter or an underscore (_), and contain only letters, numbers, and underscores. | The name cannot contain quotation marks ('), exclamation points (!), spaces, or SQL reserved keywords. |
Account | Must be 2 to 16 characters long, start with a lowercase letter, end with a lowercase letter or number, and contain only lowercase letters, numbers, and underscores (_). | - |
Password | Must be 8 to 32 characters long and contain characters from at least three of the following types: uppercase letters, lowercase letters, numbers, and special characters ( | - |
Bandwidth limits
Community-compatible edition
The cluster bandwidth depends on the ECS instance specifications and cloud disk performance.
Enterprise edition
cloud disk storage:
Type
ESSD PL1
ESSD PL2
Cluster read/write bandwidth (MB/s)
min{(120 * Number of nodes) + (0.5 * Total provisioned storage in GB), (460 * Number of nodes)}
min{(120 * Number of nodes) + (0.5 * Total provisioned storage in GB), (980 * Number of nodes)}
OSS storage:
Region
Cluster R/W bandwidth (Gb/s)
Per-node limit
CCU
Read bandwidth (Gb/s)
Write bandwidth (Gb/s)
QPS (queries per second)
China (Beijing)
China (Shanghai)
China (Hangzhou)
China (Shenzhen)
Read: 100
Write: 20
[4,8)
1.6
0.6
Read: (Max CCUs per node * 4) * 25
Write: (Max CCUs per node * 4) * 2
Burst read: (Max CCUs per node * 4) * 25 * 300
Burst write: (Max CCUs per node * 4) * 2 * 300
NoteMax CCUs per node = Upper limit of the CCU range / Number of nodes.
The number of nodes is 2 if the upper CCU limit is less than 64. If the limit is 64 or greater, the number of nodes is the upper CCU limit divided by 32.
Max memory per node (GB) = Max CCUs per node * 4.
For example, for a CCU range of [4,8), the maximum CCUs per node is 4 (calculated as 8 / 2), and the maximum memory per node is 16 GB (4 * 4).
[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)
0.5
0.5
[8,16)
0.65
0.65
[16,32)
0.8
0.8
[32,48)
1
1
[48,64)
1.3
1.3
[64,64]
1.7
1.7
Enterprise Edition clusters in other regions have the same bandwidth limits as those in China (Hong Kong).
Storage type R/W latency
Storage type | Endpoint type | Accelerator | Read RT (4 KiB, ms) | Write RT (4 KiB, ms) |
OSS (local redundancy) | Standard endpoint | No | Fluctuates between 13.8 and 14.2 | Fluctuates between 24.7 and 26.4 |
cloud disk | Not applicable | Not applicable | 1.2 | 2.6 |