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Tair:DRAM-based instances

Last Updated:Mar 25, 2024

This topic describes the specifications of Tair DRAM-based instances that are deployed in cloud disk-based mode. These specifications include the memory capacity, maximum number of connections, maximum bandwidth, and queries per second (QPS) reference value.

Instance specifications

The following tables list the specifications of individual shards. The overall performance of a cluster or read/write splitting instance can be calculated by using the following formula: Overall performance = Performance of a single shard × Number of shards.

Note
  • The ESSDs listed in these tables are used only to support the operation of the system, such as storing logs, supporting temporary file backup, and storing append-only files (AOFs). They are not intended for data storage.

  • For information about the differences between the direct connection mode and the proxy mode that are supported by cluster instances, see Cluster architecture.

  • You can adjust the number of shards for cluster instances that are deployed in cloud disk-based mode. For more information, see Adjust the number of data shards for an instance.

Shard specifications for standard instances and cluster instances in direct connection mode

The following specifications are applicable to cloud disk-based standard instances and cluster instances in direct connection mode.

Table 1. Shard specifications for standard instances and cluster instances in direct connection mode

Specification

InstanceClass value (used in API operations)

CPU cores

Memory (GB)

ESSD capacity (GB)

Bandwidth (Mbit/s)

Maximum new connections per second

Maximum connections

QPS reference value

1 GB

tair.rdb.1g

6

1

5

96

30,000

30,000

300,000

2 GB

tair.rdb.2g

6

2

10

96

30,000

30,000

300,000

4 GB

tair.rdb.4g

6

4

20

96

30,000

30,000

300,000

8 GB

tair.rdb.8g

6

8

40

96

30,000

30,000

300,000

16 GB

tair.rdb.16g

6

16

80

96

30,000

30,000

300,000

24 GB

tair.rdb.24g

6

24

120

96

30,000

30,000

300,000

32 GB

tair.rdb.32g

6

32

160

96

30,000

30,000

300,000

64 GB

tair.rdb.64g

6

64

320

96

30,000

30,000

300,000

Shard specifications for read/write splitting instances and cluster instances in proxy mode

The following specifications are applicable to cloud disk-based read/write splitting instances and cluster instances in proxy mode.

Table 2. Shard specifications for read/write splitting instances and cluster instances in proxy mode

Specification

InstanceClass value (used in API operations)

CPU cores

Memory (GB)

ESSD capacity (GB)

Bandwidth (Mbit/s)

Maximum new connections per second

Maximum connections

QPS reference value

1 GB

tair.rdb.with.proxy.1g

6

1

5

96

30,000

30,000

300,000

2 GB

tair.rdb.with.proxy.2g

6

2

10

96

30,000

30,000

300,000

4 GB

tair.rdb.with.proxy.4g

6

4

20

96

30,000

30,000

300,000

8 GB

tair.rdb.with.proxy.8g

6

8

40

96

30,000

30,000

300,000

16 GB

tair.rdb.with.proxy.16g

6

16

80

96

30,000

30,000

300,000

24 GB

tair.rdb.with.proxy.24g

6

24

120

96

30,000

30,000

300,000

32 GB

tair.rdb.with.proxy.32g

6

32

160

96

30,000

30,000

300,000

64 GB

tair.rdb.with.proxy.64g

6

64

320

96

30,000

30,000

300,000

Performance description

Architecture

Description

Standard architecture

The overall performance of standard instances is the same as that described in Table 1.

Cluster architecture in direct connection mode

Cluster architecture in proxy mode

Read/write splitting architecture

Instance performance = Shard specifications × Number of shards.

Note

When a cluster instance that runs in proxy mode is accessed, the maximum bandwidth is 2,048 Mbit/s, the maximum total QPS is 10,000,000, and the maximum number of connections is 500,000.

For example, assume that an instance has four shards of the tair.rdb.with.proxy.1g type with the following specifications:

  • Number of CPU cores: 6

  • Bandwidth: 96 Mbit/s

  • Maximum number of connections: 30,000

In this case, the instance provides the following performance:

  • Number of CPU cores: 24

  • Bandwidth: 384 Mbit/s

  • Maximum number of connections: 120,000

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.

Bandwidth description

  • Each bandwidth value in the preceding tables represents the maximum bandwidth of a single shard. The total bandwidth of a cluster or read/write splitting instance is the combined bandwidth of all shards or nodes in the instance.

  • The maximum bandwidth for a cluster instance in proxy mode or a read/write splitting instance is 2,048 Mbit/s. After the upper limit is reached, the bandwidth cannot be increased even if you add more shards or nodes to the instance. Cluster instances in direct connection mode have no limits on the overall bandwidth.

  • The bandwidth value is applicable to the upstream and downstream bandwidths. For example, if the overall bandwidth of an instance is 24 Mbit/s, the upstream and downstream bandwidths of the instance are both 24 Mbit/s.

  • 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: The maximum number of connections to an instance is 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.

  • Direct connection mode: The maximum number of connections to a single shard is 30,000. The maximum number of connections to an instance can be calculated by using the following formula: 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. For example, assume that the maximum number of new connections to an instance per second is 10,000, the maximum number of connections to the instance is 50,000, and 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 22,000. This value is calculated by using the following formula: 12,000 + 10,000.

Note

If the instance is connected in direct connection mode, connection performance degrades because proxy nodes are bypassed. The maximum number of new connections to a single data shard per second is 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.