[DRBD-user] Drbd mysql

alex at crackpot.org alex at crackpot.org
Thu Aug 23 00:49:42 CEST 2007


Quoting Lars Ellenberg <lars.ellenberg at linbit.com>:

> so replicating it using drbd and a cluster file system,
> and then simultaneously accessing it with a second mysql instance
> on a second box
> can not magically make it work.
>
> to have more than one application instance access the same data source,
> they have to coordinate access,
> whether they run on a single host, or on two different hosts.
> not only writes (that should be obvious),
> but also reads, to avoid cache coherency issues.

You can do this if you configure MySQL to use external locking.

You are limited to only MyISAM tables (no foreign keys, no  
transactions, only table-level locking).  I've used this to play  
around with running 2 MySQL daemons on the same box with the same data  
files.  I have no idea how well it performs 'for real'.  I'd be a  
little scared to find out...  But if someone feels like experimenting  
it can be done.

http://dev.mysql.com/doc/refman/5.0/en/external-locking.html

alex



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