# How to read the checksums table

**URL:** <https://forums.percona.com/t/how-to-read-the-checksums-table/37355>\
**Category:** Percona XtraDB Cluster 8.x\
**Created:** [March 25, 2025, 12:25pm UTC](https://forums.percona.com/t/how-to-read-the-checksums-table/37355 "2025-03-25T12:25:46Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![rkuijk](https://avatars.discourse-cdn.com/v4/letter/r/b4bc9f/32.png) [@rkuijk](https://forums.percona.com/u/rkuijk)\
**Post date:** [March 25, 2025, 12:25pm UTC](https://forums.percona.com/t/how-to-read-the-checksums-table/37355/1 "2025-03-25T12:25:46Z")

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Hi Everyone,

We got a percona mysql cluster and one of these servers has a physical replication to a fourth server.

We want to check if the this 4th server matches with the percona cluster.

For this we use pt-table-checksum the results of this check is written to checksums\_20250325\_Mar.

How do we read this table? What do the following columns mean. Is this described somewhere? In here I do not find it: [pt-table-checksum — Percona Toolkit Documentation](https://docs.percona.com/percona-toolkit/pt-table-checksum.html)

chunk  
chunk\_time  
chunk\_index  
lower\_boundary  
upper\_boundary  
this\_crc  
this\_cnt  
master\_crc  
master\_cnt

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<div class="post-metadata">

**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:** [March 25, 2025, 1:18pm UTC](https://forums.percona.com/t/how-to-read-the-checksums-table/37355/2 "2025-03-25T13:18:38Z")

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Hello @rkuijk,  
Run this on the replica:  
`SELECT COUNT(*), db, tbl FROM percona.checksums WHERE this_crc != master_crc GROUP BY db, tbl`

It will show you a count of the number of chunks that are different between source, and replica, grouped by db.table.

“this\_crc” and “this\_cnt” are the CRC checksum, and row counts as calculated on “this” server. If you are looking at node1, then “this” means node1. If you look at node42233, this “this” means node42233. “master\_crc” and “master\_cnt” are similar, but are a copy from the upstream source so that you can compare “this” (ie: local) to source.

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<div class="post-metadata">

**Author:** ![rkuijk](https://avatars.discourse-cdn.com/v4/letter/r/b4bc9f/32.png) [@rkuijk](https://forums.percona.com/u/rkuijk)\
**Post date:** [March 26, 2025, 9:34am UTC](https://forums.percona.com/t/how-to-read-the-checksums-table/37355/3 "2025-03-26T09:34:57Z")

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Ok great thats explains it better thank you.