Is there a relationship between TiFlash query speed and the number of replicas (one replica, two replicas, three replicas, etc.)?

Note:
This topic has been translated from a Chinese forum by GPT and might contain errors.

Original topic: tiflash查询速度和副本数(一副本、二副本、三副本等)有无关系

| username: jingyesi3401

[TiDB Usage Environment] Production Environment, Testing

[TiDB Version] 5.1.0

[Encountered Problem: Problem Phenomenon and Impact] Currently, TiFlash is set to two replicas. As the data volume gradually increases, the available disk space is decreasing. Therefore, we are planning to adjust from two replicas to one replica. Will this adjustment affect the query speed?

| username: tidb菜鸟一只 | Original post link

It does not affect the query speed, but if a single replica fails, it may impact production.

| username: Jasper | Original post link

The query speed is not related to the number of replicas; the number of replicas only affects high availability. When MPP is enabled, having more TiFlash nodes can effectively improve execution efficiency.

| username: jingyesi3401 | Original post link

Is this exception referring to one of the four nodes crashing?

| username: tidb菜鸟一只 | Original post link

Yes, if you have two replicas, it’s fine if one out of four nodes goes down, but with a single replica, it definitely won’t work.

| username: 大飞哥online | Original post link

It is to determine the degree of high availability.

| username: 像风一样的男子 | Original post link

It depends on the downtime your high availability can tolerate. If you have time to handle single replica downtime issues, then switch to single replica.

| username: jingyesi3401 | Original post link

Got it, thank you.

| username: TiDBer_小阿飞 | Original post link

The main impact is on high availability, it doesn’t affect queries.

| username: jingyesi3401 | Original post link

Okay, thank you.

| username: jingyesi3401 | Original post link

Thank you.

| username: system | Original post link

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