Read Consistency Level
Read consistency levels are the way to control the level of consistency you want to achieve when reading data from the databases. The choice of read consistency level depends on the specific requirements of your application. It is very important in determining if a read repair needs to be performed as it is not needed for all the consistency levels.
Below is the table for different Read Consistency Levels:
Read Consistency Level |
Description |
|---|---|
| ONE | Since the data from the first direct read request satisfies consistency level ONE, read repair is not necessary. No digest read requests are involved for finding mismatches in data. |
| TWO | Read repair is performed here, if inconsistencies are found in the data as determined by the direct and digest read requests |
| THREE | Read repair is performed here, if inconsistencies are found in the data as determined by the direct and digest read requests |
| LOCAL_ONE | Read repair is not performed as the data from the direct read request from the closest replica satisfies the consistency level LOCAL_ONE. No digest read requests are involved for finding mismatches in data. |
| LOCAL_QUORUM | Read repair is performed if inconsistencies in data are found as determined by the direct and digest read requests |
| QUORUM | Read repair is performed if inconsistencies in data are found as determined by the direct and digest read requests |
Read Repair Algorithm in System Design
Data replication over several nodes is used in distributed systems to ensure fault tolerance and high availability. It is possible for discrepancies to appear when data is replicated as a result of elements like node failures, network partitions, or concurrent modifications. To guarantee that every client sees the same view of the data, consistency between copies must be maintained. The read repair algorithm is a technique employed to detect and resolve such inconsistencies during read operations.
Read repair algorithm
Important Topics for Read Repair Algorithm
- Read Repair Algorithm:
- Read Consistency Level
- Advantages of Read Repair Algorithm