Isn't it? I do not have practical experience with MariaDB/MySQL in a HA setup,
but I have always thought that DRBD was one of the best choices, being a
simple and robust solution.

Yoshinori Matsunobu described available solutions with pros and cons here :

http://code.google.com/p/mysql-master-ha/wiki/Other_HA_Solutions

> I can test things, patchs, but I don't know what ... I didn't found
> WL#4925 patch
> so I can't test it.

We do not currently have any patch or plans for pre-allocation of binlog.

This morning I've removed DRBD to verify that it is not the bottleneck, and .... It's much faster with DRBD !

I didn't found anywere if Bug#13669 (http://bugs.mysql.com/bug.php?id=13669) was fixed, but it's seems to, as I see Binlog_commits =~ Binlog_group_commits. So I still have performance problems and perhaps WL#4925 could help .... or I'll have to buy some better hardware.