When read/write splitting is set to automatic weight allocation, ApsaraDB RDS for SQL Server assigns a fixed read weight to each read-only instance based on its instance type. The weight value determines the proportion of read traffic routed to that instance — a higher weight means a larger share of read requests.
Note
Configure the weight allocation mode when you enable the read/write splitting endpoint. To override the defaults, modify the read weight at any time.
Read-only instances support the general-purpose instance family and the dedicated instance family. For details, see Instance families.
General-purpose instance family
| Instance type | CPU cores | Memory | Default weight |
|---|---|---|---|
| mssql.x4.medium.ro | 2 | 8 GB | 800 |
| mssql.x4.large.ro | 4 | 16 GB | 1,600 |
| mssql.x4.xlarge.ro | 8 | 32 GB | 3,200 |
| mssql.x4.2xlarge.ro | 16 | 64 GB | 6,400 |
| mssql.x4.4xlarge.ro | 32 | 128 GB | 9,900 |
| mssql.x4.8xlarge.ro | 64 | 256 GB | 9,900 |
| mssql.x8.medium.ro | 2 | 16 GB | 1,600 |
| mssql.x8.large.ro | 4 | 32 GB | 3,200 |
| mssql.x8.xlarge.ro | 8 | 64 GB | 6,400 |
| mssql.x8.2xlarge.ro | 16 | 128 GB | 9,900 |
| mssql.x8.4xlarge.ro | 32 | 256 GB | 9,900 |
| mssql.x10.5xlarge.ro | 40 | 384 GB | 9,900 |
| mssql.x8.8xlarge.ro | 64 | 512 GB | 9,900 |
General-purpose instance family
| Instance type | CPU cores | Memory | Default weight |
|---|---|---|---|
| rds.mssql.s3.large | 4 | 8 GB | 800 |
| rds.mssql.c1.large | 8 | 16 GB | 1,600 |
| rds.mssql.m1.medium | 4 | 16 GB | 1,600 |
| rds.mssql.c1.xlarge | 8 | 32 GB | 3,200 |
| rds.mssql.c2.xlarge | 16 | 64 GB | 6,400 |
| rds.mssql.c4.xlarge | 32 | 128 GB | 9,900 |
| rds.mssql.c4.2xlarge | 32 | 256 GB | 9,900 |