

Moving 6 Billion Messages Without Being Noticed - kachnuv_ocasek
http://dt.deviantart.com/art/Moving-6-Billion-Messages-Without-Being-Noticed-285571516

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waitwhat
They needed the Percona toolkit (previously Maatkit).
[http://www.percona.com/doc/percona-toolkit/2.0/pt-table-
sync...](http://www.percona.com/doc/percona-toolkit/2.0/pt-table-sync.html)

~~~
kfool
The toolkit documentation reports limitations.

What they really needed is ChronicDB <http://chronicdb.com>

~~~
newman314
If you are going to flog ChronicDB, please at least disclose if you have some
sort of relationship with said company. Most of your previous submissions
pertain to ChronicDB.

~~~
kfool
Sorry for not disclosing I work on ChronicDB.

The author of the 6b article kindly provided more information about the time
it took for the migration:

<http://news.ycombinator.com/item?id=3621561>

A couple of limitations of the Percona tool are related to changing data in
tables with ON DELETE and ON UPDATE foreign key constraints and possible lock-
ups of tables. It is a bi-directional replication tool, so it has to deal with
the master-master replication case and as such does not guarantee data
consistency.

Still the tool is helpful in many cases and congrats to Percona for developing
it. Replication safety is a non-trivial problem in general.

~~~
waitwhat
They weren't doing a master-master sync.

