# Guidance needed for pt-table-checksum on MySQL master-master / source-source replication

**URL:** <https://forums.percona.com/t/guidance-needed-for-pt-table-checksum-on-mysql-master-master-source-source-replication/41142>\
**Category:** Other MySQL® Questions\
**Tags:** mysql, percona\
**Created:** [August 6, 2026, 3:48am UTC](https://forums.percona.com/t/guidance-needed-for-pt-table-checksum-on-mysql-master-master-source-source-replication/41142 "2026-08-06T03:48:29Z")\
**Posts on this page:** 1\
**Showing post:** 4

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**Author:** ![matthewb](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/matthewb/32/34_2.png) [@matthewb](https://forums.percona.com/u/matthewb)\
**Post date:** [August 17, 2026, 3:34pm UTC](https://forums.percona.com/t/guidance-needed-for-pt-table-checksum-on-mysql-master-master-source-source-replication/41142/4 "2026-08-17T15:34:17Z")

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> [@degokul](#):
>
> intentionally configured in a bidirectional / source-source setup, and both nodes are expected to accept writes as part of the application design.

That’s a bad design, and goes complety opposite of established best practices.

> [@degokul](#):
>
> 1. In a true bidirectional writable topology

That’s not what S/S replication is. S/S is technically 2 **separate** channels of one-way replication. There is no bidirectional replication in MySQL. (bidirectional implies a single communications channel with information flowing in both directions) A write on node1 is transactionally, and globally isolated from a transaction on node2.

If you want that level of communication, you should upgrade to Percona XtraDB Cluster, or use Group Replication. Both of those use a single channel for replication/communication where transactions are coordinated across all nodes.

> [@degokul](#):
>
> 1. how do you recommend interpreting “source” and “replica” roles for checksum runs

Even in S/S, node1(s)-\>node2(r) and node2(s)-\>node1(r). As above, it is **not** bidirectional; there are two separate channels.

> [@degokul](#):
>
> If source-source dual-write is outside the intended operating model of pt-table-checksum

It is not. pt-t-c works perfectly in S/S configurations. In reading this post, I see more confusion and misunderstanding about S/S replication, than using pt-t-c.

See my answers in [your other post](https://forums.percona.com/t/best-practice-for-pt-table-checksum-frequency-in-oracle-unified-assurance-active-active-mysql-setup/41144/2).

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