Yoshinori Matsunobu sparked some interest recently when he posted about his MySQL MHA HA solution, and there has been some discussion of it internally at Yahoo compared with the standard we currently have.  

Full disclosure:  I haven’t read every bit of the documentation or tried it out yet, so I apologize in advance to Yoshinori if I mistakenly represent his hard work. 

I see a lot of great ideas in Yoshinori’s release, it seems to focus on two main problems:

1. A process to monitor an active master and perform a failover when it fails
2. The bit that finds the most “caught-up” slave and distributes …

There are times when what you have is a partially running database and a bunch of backup innodb tablespace files (the .ibd files). If you're using innodb_file_per_table, then you have a separate .ibd file for each InnoDB table.

Now, you have your running database with a bunch of tables, and you want to replace some of them with the backup .ibd files. According to the MySQL docs, you'd do this:

1. ALTER TABLE foo DISCARD TABLESPACE; (this deletes the current .ibd file)
2. copy the old .ibd file into your database directory
3. ALTER TABLE foo IMPORT TABLESPACE;
   

Assuming your .ibd file was from the same database and you did not drop the table and recreate it sometime between when you made the backup .ibd and now, this should work. Except... if …