specifications of Tair DRAM-based cluster instances - Tair

This topic describes the specifications of Tair DRAM-based cluster instances. These specifications include the memory capacity, maximum number of connections, maximum bandwidth, and queries per second (QPS) reference value.

Instance specifications

Instance specification types: 2 shards, 4 shards, 8 shards, 16 shards, 32 shards, 64 shards, 128 shards, and 256 shards.

2 shards

For this series of instance specifications, the number of shards is 2, the number of CPU cores is 12 (6 cores per shard), and the maximum number of new connections per second is 50,000.

Specification	InstanceClass value (used in API operations)	Memory per shard (GB)	Proxy mode: Maximum connections	Direct connection mode: Maximum connections	Total bandwidth (Mbit/s)	Bandwidth per shard (Mbit/s)	QPS reference value
2 GB cluster instance (2 shards)	redis.amber.logic.sharding.1g.2db.0rodb.6proxy.multithread	1	480,000	60,000	192	96	480,000
4 GB cluster instance (2 shards)	redis.amber.logic.sharding.2g.2db.0rodb.6proxy.multithread	2	480,000	60,000	192	96	480,000

4 shards

For this series of instance specifications, the number of shards is 4, the number of CPU cores is 24 (6 cores per shard), and the maximum number of new connections per second is 50,000.

Specification	InstanceClass value (used in API operations)	Memory per shard (GB)	Proxy mode: Maximum connections	Direct connection mode: Maximum connections	Total bandwidth (Mbit/s)	Bandwidth per shard (Mbit/s)	QPS reference value
8 GB cluster instance (4 shards)	redis.amber.logic.sharding.2g.4db.0rodb.12proxy.multithread	2	500,000	120,000	384	96	960,000

8 shards

For this series of instance specifications, the number of shards is 8, the number of CPU cores is 48 (6 cores per shard), and the maximum number of new connections per second is 50,000.

Specification	InstanceClass value (used in API operations)	Memory per shard (GB)	Proxy mode: Maximum connections	Direct connection mode: Maximum connections	Total bandwidth (Mbit/s)	Bandwidth per shard (Mbit/s)	QPS reference value
16 GB cluster instance (8 shards)	redis.amber.logic.sharding.2g.8db.0rodb.24proxy.multithread	2	500,000	240,000	768	96	1,920,000
32 GB cluster instance (8 shards)	redis.amber.logic.sharding.4g.8db.0rodb.24proxy.multithread	4	500,000	240,000	768	96	1,920,000
64 GB cluster instance (8 shards)	redis.amber.logic.sharding.8g.8db.0rodb.24proxy.multithread	8	500,000	240,000	768	96	1,920,000

16 shards

For this series of instance specifications, the number of shards is 16, the number of CPU cores is 96 (6 cores per shard), and the maximum number of new connections per second is 50,000.

Specification	InstanceClass value (used in API operations)	Memory per shard (GB)	Proxy mode: Maximum connections	Direct connection mode: Maximum connections	Total bandwidth (Mbit/s)	Bandwidth per shard (Mbit/s)	QPS reference value
128 GB cluster instance (16 shards)	redis.amber.logic.sharding.8g.16db.0rodb.48proxy.multithread	8	500,000	480,000	1,536	96	3,840,000
256 GB cluster instance (16 shards)	redis.amber.logic.sharding.16g.16db.0rodb.48proxy.multithread	16	500,000	480,000	1,536	96	3,840,000

32 shards

For this series of instance specifications, the number of shards is 32, the number of CPU cores is 192 (6 cores per shard), and the maximum number of new connections per second is 50,000.

Specification	InstanceClass value (used in API operations)	Memory per shard (GB)	Proxy mode: Maximum connections	Direct connection mode: Maximum connections	Total bandwidth (Mbit/s)	Bandwidth per shard (Mbit/s)	QPS reference value
512 GB cluster instance (32 shards)	redis.amber.logic.sharding.16g.32db.0rodb.96proxy.multithread	16	500,000	960,000	2,048	96	7,680,000

64 shards

For this series of instance specifications, the number of shards is 64, the number of CPU cores is 384 (6 cores per shard), and the maximum number of new connections per second is 50,000.

Specification	InstanceClass value (used in API operations)	Memory per shard (GB)	Proxy mode: Maximum connections	Direct connection mode: Maximum connections	Total bandwidth (Mbit/s)	Bandwidth per shard (Mbit/s)	QPS reference value
1024 GB cluster instance (64 shards)	redis.amber.logic.sharding.16g.64db.0rodb.192proxy.multithread	16	500,000	1,920,000	2,048	96	15,360,000

128 shards

For this series of instance specifications, the number of shards is 128, the number of CPU cores is 768 (6 cores per shard), and the maximum number of new connections per second is 50,000.

Specification	InstanceClass value (used in API operations)	Memory per shard (GB)	Proxy mode: Maximum connections	Direct connection mode: Maximum connections	Total bandwidth (Mbit/s)	Bandwidth per shard (Mbit/s)	QPS reference value
2048 GB cluster instance (128 shards)	redis.amber.logic.sharding.16g.128db.0rodb.384proxy.multithread	16	500,000	3,840,000	2,048	96	30,720,000

256 shards

For this series of instance specifications, the number of shards is 256, the number of CPU cores is 1,536 (6 cores per shard), and the maximum number of new connections per second is 50,000.

Specification	InstanceClass value (used in API operations)	Memory per shard (GB)	Proxy mode: Maximum connections	Direct connection mode: Maximum connections	Total bandwidth (Mbit/s)	Bandwidth per shard (Mbit/s)	QPS reference value
4096 GB cluster instance (256 shards)	redis.amber.logic.sharding.16g.256db.0rodb.768proxy.multithread	16	500,000	7,680,000	2,048	96	61,440,000

Notes about CPU cores

To ensure service stability, the system reserves a CPU core to process background tasks. In a cluster instance or a read/write splitting instance, the system reserves a CPU core for each data shard or each read replica to process background tasks.

Calculation rules for bandwidth values

Each bandwidth value in the preceding tables represents the maximum bandwidth for an instance of the corresponding instance type, which is the combined bandwidth of all shards or nodes in the instance. The maximum bandwidth for each shard is 96 Mbit/s.
If the default proxy endpoint is used by a cluster instance, the maximum bandwidth for the cluster instance is 2,048 Mbit/s. After the upper limit is reached, the bandwidth cannot be increased even if you add more shards to the cluster instance.
Note
To handle network traffic peaks, you can enable the direct connection mode. For more information, see Enable the direct connection mode. The direct connection mode is applicable only to cluster instances. In direct connection mode, the maximum bandwidth of the instance is equal to the maximum bandwidth of a single shard multiplied by the number of shards. For example, if a cluster instance contains 128 shards and each shard is allocated a memory of more than 1 GB, the maximum bandwidth of the instance is 12,288 Mbit/s.
The bandwidth value is applicable to the upstream and downstream bandwidths. For example, if the bandwidth of an instance is 10 Mbit/s, the upstream and downstream bandwidths of the instance are both 10 Mbit/s.
Note
If your instance may experience an unexpected or anticipated surge in traffic, you can adjust the bandwidth of the instance on demand. For more information, see Manually increase the bandwidth of an instance.
The bandwidth limits of Tair and Redis refer to the data transfer capacity of individual shards within their respective distributed systems. The limits are generally independent of the network connection types used by clients to connect to the shards.

For information about the FAQ about bandwidth, see FAQ about bandwidth.

Calculation rules for connections

Item

Description

Maximum number of connections

Proxy mode: 500,000. If the upper limit of 500,000 connections is reached, subsequent connections cannot be established even if you add more shards or nodes.
Note
When you run a specific Pub/Sub, blocking, or transaction command on a cluster instance in proxy mode, the system establishes a dedicated backend connection for your client. In this case, the maximum number of connections to the instance is subject to the maximum number of connections to a single shard in direct connection mode. This is because the connections cannot be aggregated in this scenario.
Direct connection mode: 30,000 for a single shard. Maximum number of connections to an instance = Number of shards × 30,000.

Number of new connections per second

The maximum number of new connections per second refers to the number of connections that can be established per second.

Proxy mode: 50,000. For example, assume that the actual number of connections at the Nth second after the instance starts to run is 12,000. In this case, at the (N+1)th second, the maximum number of connections is 62,000. This value is calculated by using the following formula: 12,000 + 50,000.
Note
When you run a specific Pub/Sub, blocking, or transaction command on a cluster instance in proxy mode, the actual number of new connections to the instance per second is subject to the maximum number of connections to a single shard in direct connection mode.
Direct connection mode: 2,000. For example, if an instance has four data shards, the maximum number of new connections to the instance per second is 8,000.

FAQ

Why is the maximum number of connections to my instance different from that described in this topic?
The maximum number of connections of specific instance types may be adjusted after the service is upgraded. If the maximum number of connections to your instance is different from that described in this topic, change the configurations of your instance to update the bandwidth. Make sure that you select the same instance type when you change the configurations. For more information, see Change the configurations of an instance.
Why am I unable to write data to a cluster instance when instance memory is not exhausted?
This is because the instance contains exhausted data shards. ApsaraDB for Redis uses the hash algorithm to evenly write data to different data shards. If the instance contains large keys, resources are unevenly distributed in the instance and the data shards that house these large keys may even be exhausted. In this case, specific write requests to the instance may fail.
You can use the Performance Monitor feature to check and optimize the performance of each data shard. For more information, see How do I view the performance metrics such as memory usage of each child node in an ApsaraDB for Redis cluster instance?