This topic describes the specifications of ApsaraDB for Redis Enhanced Edition (Tair) DRAM-based instances that use cloud disks. These specifications include the memory capacity, maximum number of connections to each instance, maximum bandwidth, and queries per second (QPS) reference value.

Note For more information about instances that use local disks and those that use cloud disks, see Comparison between ApsaraDB for Redis instances that use local disks and those that use cloud disks.

Performance

The specifications in this topic are applicable to DRAM-based instances in the standard architecture or cluster architecture.

Architecture Performance
Standard The overall performance of standard instances is as described in the preceding Instance types table.
Cluster The overall performance of cluster instances equals the number of shards multiplied by the performance of each shard specified by shard specifications.
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. To handle ultra-high network traffic for your business, you can enable the direct connection mode. For more information, see Enable the direct connection mode.
For example, a cluster instance has four shards of the tair.rdb.256m type. This type is the first instance type in the Instance types table. The following items show the performance of each shard:
  • CPU cores: 6 cores
  • Bandwidth: 96 Mbit/s
  • Maximum number of connections: 30,000

The cluster instance provides the following performance:

  • CPU cores: 24 cores
  • Bandwidth: 384 Mbit/s
  • Maximum number of connections: 120,000

Instance types

Note Enhanced SSDs (ESSDs) are used only to store system operating data, such as logs and backup data. ESSDs are not used as the media to read or write data. For more information about ESSDs, see ESSDs.
Table 1. Instance types
Instance type InstanceClass value (used in API operations) Number of CPU cores Memory (GB) ESSDs capacity (GB) Number of I/O threads Maximum bandwidth (Mbit/s) Number of new connections per second Maximum number of concurrent connections QPS reference value
256 MB tair.rdb.256m 6 0.25 1.25 4 96 30,000 30,000 300,000
1 GB tair.rdb.1g 6 1 5 4 96 30,000 30,000 300,000
2 GB tair.rdb.2g 6 2 10 4 96 30,000 30,000 300,000
4 GB tair.rdb.4g 6 4 20 4 96 30,000 30,000 300,000
8 GB tair.rdb.8g 6 8 40 4 96 30,000 30,000 300,000
16 GB tair.rdb.16g 6 16 80 4 96 30,000 30,000 300,000
24 GB tair.rdb.24g 6 24 120 4 96 30,000 30,000 300,000
32 GB tair.rdb.32g 6 32 160 4 96 30,000 30,000 300,000
64 GB tair.rdb.64g 6 64 320 4 96 30,000 30,000 300,000

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

  • The bandwidth value applies 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.
  • The bandwidth column in the preceding Instance types table represents the internal bandwidth of Tair instances. The public bandwidth is determined by the internal bandwidth and is limited by the bandwidth of the connection between a Tair instance and a client. To ensure higher security and lower network latency, we recommend that you connect to a What is a VPC? instance over a virtual private cloud (VPC). For more information about VPCs, see Tair

Notes on connections

The maximum number of new connections per second affects the maximum number of connections at a specific second. For example, assume that the maximum number of new connections per second of an instance is 10,000 and the maximum number of connections of the instance is 50,000. 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.