Comments on: Oh dear MySQL slave, where did you put those rows?

By: Sunny Walia

Sunny Walia — Sat, 24 May 2008 07:49:23 +0000

From all the people I have talked to (mostly mysql consultants), they have never had issues with mk-table-checksum running on any of the dbs they used it on. I really don’t think I need to be concerned with the size at this time. Since Baron mentioned 100gb of data and none of my dbs are there (biggest one is close to 40 gigs), I will use this tool until I start to see performance issues.

By: Xaprb

Xaprb — Sat, 24 May 2008 01:36:26 +0000

Well… define small. That means different things to different people. The mk-table-checksum tools are suitable for 100GB or so of data, depending on your performance needs.

By: Sunny Walia

Sunny Walia — Mon, 19 May 2008 02:56:16 +0000

Frank: what do you use for large databases if that tool is not suitable for it?

Xaprb/Mark: Thanks for you comments. Good to know it is not something I mis configured and it is a known issue.

By: Frank Mashraqi

Frank Mashraqi — Sun, 18 May 2008 14:58:15 +0000

This is why you can never trust slaves. Maatkit is a very valuable tool but only suitable for small-medium sized databases.

By: Mark Robson

Mark Robson — Sat, 17 May 2008 14:16:27 +0000

You MUST monitor mysql slaves all the time using something such as mk-table-checksum – otherwise there is no guarantee they will stay in sync even if initially there.

There are many possible reasons for this, the mysql manual explains some of them. Most of them are to do with the application’s design, others are shortcomings in mysql itself.

Using row-based replication on 5.1 + might be better, but it still won’t be guaranteed – you’ll want to continue checking.

Mark

By: Xaprb

Xaprb — Sat, 17 May 2008 11:42:56 +0000

Alas, no you cannot trust slaves. You must check them. Hence Maatkit: mk-table-checksum and mk-table-sync.