This topic describes the available instance types in ApsaraDB for MongoDB. The historical instance types are also listed.
New Instance types
Due to the updates of physical resources, since July 10, 2017, the following types
of ApsaraDB for MongoDB instances are used.
Note The supported memory capacity of each instance type includes the memory that is occupied
by management services by ApsaraDB for MongoDB, the database service, and the underlying
operating system (such as the BIOS, the kernel of the operating system, and the hypervisor).
Therefore, the available memory may be less than the memory capacity that is supported
by the instance type.
Historical instance types
For more information about historical instance types, see Historical instance types.
Maximum IOPS for standard SSDs and ESSDs
The IOPS of a local SSD is tied to the instance type. The IOPS of an enhanced SSD (ESSD) is proportional to the storage capacity. The Elastic Compute Service (ECS) instance type also limits the maximum IOPS.
The IOPS of an ESSD is calculated based on the following formula:
min {1,800 + 50 × Storage capacity, 50000, ECS-limited IOPS}Note If the throughput of an instance reaches the upper limit, the IOPS of the instance
decreases. For more information, see Storage I/O performance of new-generation enterprise-level instance families.
Description of the values in the preceding formula:
1,800 + 50 × Storage capacity: the basic calculation formula for the IOPS of the ESSD.50,000: the maximum IOPS of a single PL1 ESSD. For more information, see ESSDs.ECS-limited IOPS: the maximum IOPS of the ECS instance type. For the maximum IOPS of each instance type, see the New Instance types section in this topic.
The actual IOPS of an instance is the minimum of the three values. Examples:
- The storage capacity of an instance is 20 GB. The actual IOPS of the instance is 2,800 (1,800 + 50 × 20).
- If the instance type is
mdb.shard.2x.xlarge.d, the ECS-limited IOPS is 21,000. If the storage capacity of the instance is 6,000 GB, the calculated IOPS of the instance is 301,800, which exceeds the maximum IOPS of a single PL1 ESSD and the ECS-limited IOPS. In this case, the actual IOPS of the instance is 21,000.
Instance categories
The maximum number of connections and maximum IOPS of an RDS instance vary based on
the instance category. In practice, an instance may fail to deliver the maximum number
of connections or maximum IOPS due to various reasons. The following list describes
the instance categories.
| Category | Description | Maximum number of connections guaranteed | Maximum IOPS guaranteed |
|---|---|---|---|
| Dedicated cloud disk instance | Occupies exclusive CPU, memory, storage media, and I/O resources. | Yes | Yes |
| Dedicated host RDS instance | Occupies exclusive CPU, memory, storage media, and I/O resources. | Yes | Yes |
| Dedicated local disk instance | Occupies exclusive CPU and memory and share I/O resources with other instances on the same physical server. | Yes | No |
| General-purpose RDS instance | Occupies exclusive memory and share CPU and I/O resources with other instances on the same physical server. | Yes | No |
Note For more information, see Instance categories.