In the DTS data sync task configuration, or when the task is running, the task concurrency number and RPS can be flexibly adjusted based on the data write volume of the source database, and the resource configuration of both the source and target databases.
Note:
This document only provides guidelines for operating DTS performance parameters. To comprehensively enhance the DTS transmission performance, it is necessary to analyze the load and network conditions of the source/target, etc. For details, see DTS Performance Tuning Best Practices.
Application Scope
Data sync link between MySQL/MariaDB/Percona/TDSQL-C MySQL/TDSQL MySQL.
Notes
1. You can only adjust the speed during the task configuration process, or when the task status is Running.
2. When reducing the task speed, please observe the delay data volume and delay time. DTS by default only caches the intermediate data for 7 days. A long-term large delay volume may cause the intermediate cache data to expire and the task to fail completely.
3. Adjusting the speed during the full export stage will cause the task to restart, and a partial restart may require starting the sync all over again, as follows.
MySQL series data sync tasks default to lock-free sync. In lock-free sync scenarios, during the structure export stage and the non-primary key table export stage, restarting the task requires starting all over again; and during the primary key table export stage, restarting the task will resume sync, without the need to start all over again.
3.1 Restart during full export stage
During the structure export stage and the non-primary key table export stage, restarting the task requires starting all over again;
During the primary key table export stage: If the time from the start of sync (X) to the time the retry operation is performed (Y) is within 48 hours (including 48 hours), breakpoint resume is supported. If it exceeds 48 hours, the task needs to start all over again. Once the task retries or automatically restarts and begins sync from scratch, the time X will be recalculated.
3.2 Restart during full import and incremental sync stages: support breakpoint resume, which does not affect data transfer.
Adjustment Principles
The default number of concurrent threads for a DTS task's full export is 8, which generally does not need to be modified. If adjustment is necessary, please combine monitoring indicators and source/target database configurations, and considering the precondition of not affecting the performance of the source/target database, enhance the DTS transfer speed to the greatest extent.
DTS transfer performance is related to the configuration of the source/target database, DTS task specifications, network latency, network bandwidth, etc. Therefore, when improving DTS transfer performance, simply increasing the number of threads or RPSes may not be effective. It is necessary to analyze where the performance bottleneck lies and solve the specific problem accordingly.
Task Stage
Adjust Scenario
Adjustment Plan
Adjustment Result
Task Configuration Stage
Source database configuration is too low to handle the increased load from DTS, resulting in the source database crashing after the DTS task starts.
Reduce the number of export threads for the source database to lower the export RPS.
Valid.
Target database configuration is too low to handle the increased load from DTS, resulting in the target database crashing after the DTS task starts.
Reduce the number of import threads for the target database to lower the import RPS.
Valid.
Full Volume Stage
Source/target database configuration is high, yet DTS full volume transfer speed is slow
If the source database configuration is high, increase the number of export threads for the source database
If the target database configuration is high, increase the number of import threads for the target database.
The default RPS is very large in the full volume stage, and generally, there's no need to adjust the RPS to increase the transfer speed.
It may not always be effective.
If adjustments do not take effect, please investigate factors such as network latency and bandwidth, as these can also affect the transfer performance.
Target database configuration is low, and DTS writes to the target database too quickly, impacting the target database load (e.g., high CPU occupancy rate)
Reduce the number of import threads for the target database to lower the import RPS.
Valid.
Incremental Stage
Source database configuration is high, source database write data volume is large, and network latency is high
Check if the number of RPSes has reached the upper limit. Different specifications of DTS tasks correspond to different RPS upper limits.
If the number of RPSes has reached the upper limit, first upgrade the DTS task specifications (through Configuration Adjustment operation).
If the upgrade task does not take effect, please investigate factors such as network latency and bandwidth, as these can also affect the transfer performance.
Target database configuration is low, and DTS writes to the target database too quickly, impacting the target database load (e.g., high CPU occupancy rate)
1. Reduce the DTS task specification.
2. Decrease the concurrent thread count for importing into the target database.
Valid.
The target database configuration is low, DTS has too many connections, and the target database reaches the thread limit
Reduce the number of threads for target database import.
Valid.
DTS writes to the target database, causing lock contention with the database's own writes (e.g., lock wait timeout error)
Reduce the number of threads for importing into the target database to minimize the lock competition.
Valid.
Speed Adjustment in Task Configuration
During the initial configuration stage of the sync task, in the Advanced Options on the Set sync options and objects page, you can set the transfer speed parameters.
Speed Adjustment When the Task Is Running
You can adjust the speed during the full data sync stage by adjusting the speed parameters for both full and incremental (full export thread count and RPS, full import thread count and RPS, and incremental import thread count). During the incremental data sync stage, only the incremental speed parameters (incremental import thread count) can be modified, with specific operations as follows.
1. Log in to the DTS console, choose Data Sync page in the left sidebar, and select the specified sync task.
2. Adjust the speed during the full data sync stage.
In the Operation column, select More > Limit Speed.
Adjust the speed parameters in the pop-up interface, and click OK after completion.
3. Adjust the speed during the incremental data sync stage.
In the Operation column, select More > Limit Speed.
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