From: Dan Nelson
Date: September 12 2009 10:23pm
Subject: Re: InnoDB doubles size when converting from MyIsam
List-Archive: http://lists.mysql.com/mysql/218709
Message-Id: <20090912222354.GD54762@dan.emsphone.com>
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In the last episode (Sep 12), Arthur Meeks Meeks said:
> I have a database with about 1000 tables and 150GB. I have done a simple
> "for f in $(cat tables); do mysql -uuser -ppassword database_name -e
> "alter table $f engine=InnoDB;" ; done
> 
> I took about 3 hours and everything went fine, but I just realised that
> the same database in another server in myisam is about 150GB and in the
> server where I converted it to innodb it's about 350GB.
> 
> Is that normal?

Yes; innodb tables will require quite a bit more space than myisam, because
the table data itself is stored as an index (which means each page will be
between 50% and 94% full), and because each row needs extra space to hold
transaction and locking info.

http://dev.mysql.com/doc/refman/5.1/en/dynamic-format.html

http://dev.mysql.com/doc/refman/5.1/en/innodb-physical-structure.html
http://dev.mysql.com/doc/refman/5.1/en/innodb-physical-record.html

-- 
	Dan Nelson
	dnelson@stripped