Why Is the Capacity or Performance of a Shard of a Redis Cluster Instance Overloaded When That of the Instance Is Still Below the Bottleneck?
Redis Cluster uses a special data sharding method. Every key is part of a hash slot, which is held by a node in the cluster. To compute what is the hash slot of a given key:
- Take the CRC16 of the key modulo 16384.
- Based on the mapping between hash slots and shards, connections are redirected to the right node for data read and write operations.
Therefore, keys are not evenly distributed to each shard of an instance. If a shard contains a big key or a hot key, the capacity or performance of the shard will be overloaded, but the load on other shards is still low. As a result, the capacity or performance bottleneck of the entire instance is not reached.
Redis Usage FAQs
- Can I Change the CPU Architecture?
- Can I Change the AZ for an Instance?
- Can I Change the VPC and Subnet for a DCS Redis Instance?
- Can I Customize or Change the Port for Accessing a DCS Instance?
- Can I Modify the Connection Addresses for Accessing a DCS Instance?
- Why Do I Fail to Delete an Instance?
- Why Does It Take a Long Time to Start a Cluster DCS Instance?
- What Should I Do If an Error Occurs in redis_exporter?
- What Is Reserved Memory? How Do I Configure Reserved Memory?
- Why Is Available Memory Smaller Than Instance Cache Size?
- Why Is Redisson Distributed Lock Not Supported by DCS Proxy Cluster Redis 3.0 Instances?
- Does DCS for Redis Provide Backend Management Software?
- Can I Recover Deleted Data of a DCS Instance?
- Why Is Available Memory of Unused DCS Instances Less Than Total Memory and Why Is Memory Usage of Unused DCS Instances Greater Than Zero?
- How Do I Estimate Redis Memory Usage?
- Why Is the Capacity or Performance of a Shard of a Redis Cluster Instance Overloaded When That of the Instance Is Still Below the Bottleneck?
- Why Does an OOM Error Occur During a Redis Connection?
- What Clients Can I Use for Redis Cluster in Different Programming Languages?
- Why Do I Need to Configure Timeout for Redis Cluster?
- Why Am I Seeing a Timeout Error When Reading Data from Redis?
- Explaining and Using Hash Tags
- Why Does a Key Disappear in Redis?
- Will Cached Data Be Retained After an Instance Is Restarted?
- How Do I Know Whether an Instance Is Single-DB or Multi-DB?
- What Are the Constraints on Implementing Multi-DB on a Proxy Cluster Instance?
- How Do I Buy a Multi-DB Proxy Cluster Instance?
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