This topic describes the specifications of Tair persistent memory-optimized instances. These specifications include the memory capacity, maximum number of connections, and maximum bandwidth.
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.
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 of standard instances and cluster instances in direct connection mode
The following specifications are applicable to standard instances and cluster instances in direct connection mode.
Table 1. Shard specifications of standard instances and cluster instances in direct connection mode
Specification type | InstanceClass value (used in API operations) | Specifications | Maximum connections | Maximum bandwidth (Mbit/s) | QPS reference value | ||
CPU cores | Persistent memory (GB) | ESSD capacity (GB) | |||||
4 GB | tair.scm.standard.1m.4d | 3 | 4 | 12 | 10,000 | 96 | 100,000 |
8 GB | tair.scm.standard.2m.8d | 3 | 8 | 24 | 10,000 | 96 | 100,000 |
16 GB | tair.scm.standard.4m.16d | 3 | 16 | 48 | 10,000 | 96 | 100,000 |
32 GB | tair.scm.standard.8m.32d | 3 | 32 | 96 | 10,000 | 96 | 100,000 |
64 GB | tair.scm.standard.16m.64d | 3 | 64 | 192 | 10,000 | 96 | 100,000 |
The 4 GB specification type is unavailable for cluster instances in direct connection mode.
Shard specifications of cluster instances in proxy mode and read/write splitting instances
The following specifications are applicable to cluster instances in proxy mode and read/write splitting instances.
Table 2. Shard specifications of cluster instances in proxy mode and read/write splitting instances
Specification type | InstanceClass value (used in API operations) | Specifications | Maximum connections | Maximum bandwidth (Mbit/s) | QPS reference value | ||
CPU cores | Persistent memory (GB) | ESSD capacity (GB) | |||||
8 GB | tair.scm.with.proxy.standard.2m.8d | 3 | 8 | 24 | 10,000 | 96 | 100,000 |
16 GB | tair.scm.with.proxy.standard.4m.16d | 3 | 16 | 48 | 10,000 | 96 | 100,000 |
32 GB | tair.scm.with.proxy.standard.8m.32d | 3 | 32 | 96 | 10,000 | 96 | 100,000 |
64 GB | tair.scm.with.proxy.standard.16m.64d | 3 | 64 | 192 | 10,000 | 96 | 100,000 |
Performance description
Architecture | Description |
The overall performance of standard instances is the same as that described in Table 1. | |
Cluster architecture in direct connection mode | 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.scm.with.proxy.standard.2m.8d type. Each shard has the following specifications:
In this case, the instance provides the following performance:
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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 |
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Maximum 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 allowed 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, the maximum number of connections at the (N+1)th second 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. |