Comments on: Differences Between innodb_data_file_path and innodb_file_per_table

By: herodiade

herodiade — Sat, 29 Nov 2008 12:14:02 +0000

Actually, you can spread the ibdata files on different places (ie. several raid 10 arrays) just as with innodb_file_per_table.

This is just a matter of setting :
innodb_data_home_dir =
innodb_data_file_path = /d1/ibdata1:1024M;/d2/ibdata2:1024M;/d3/ibdata3:1024M:autoextend

In my opinion, the real case for innodb_file_per_table is the infamous “innodb ibdata files do not shrink” bug.

By: ILD

ILD — Wed, 06 Aug 2008 20:33:45 +0000

Here is my.cnf
datadir = /data/mysql
innodb_data_home_dir = /data/mysql
innodb_data_file_path = ibdata1:50M;ibdata2:50M:MAX:100M
innodb_file_per_table

The above disables innodb.
When I have the following in my.cnf
datadir = /data/mysql
innodb_file_per_table

It correctly enables innodb and it produces individual ibd tables but it winds up with the following default attribute:

innodb_data_file_path = ibdata1:10M:autoextend

How can I turn this off and still have innodb enabled with the innodb_file_per_table turned on?

This seems to be a bug.

Here is the version I am working with
mysql Ver 14.12 Distrib 5.0.36sp1, for unknown-linux-gnu (x86_64) using readline 5.0

By: ICD

ICD — Wed, 06 Aug 2008 20:27:47 +0000

ON a version 5.0.36sp1-enterprise-gpl MySQL Enterprise Server (GPL)

I have the innodb_file_per_table set on without the innodb_data_file_path set and the
following is true when I check the global variables:
have_innodb has a value of YES
innodb_data_file_path has a value of ibdata1:10M:autoextend
innodb_file_per_table has a value of ON

this to me seems to be a bug. If there will be individual file ibd files why would I have an ibdata1 created? Secondly, anytime I try setting the innodb_data_file_path it turns off the innodb engine and have_innodb winds up having a value of NO. The error when I do set the innodb_data_file_path is
080805 7:16:57 [ERROR] InnoDB: syntax error in innodb_data_file_path

Here is the entry in the my.cnf:
datadir = /data/mysql
innodb_data_home_dir = /data/mysql
innodb_data_file_path = ibdata1:50M;ibdata2:50M:MAX:100M
innodb_file_per_table

Any ideas. I want to have the .ibd per table and not have an ibdata1 which autoextends.

By: Dieter

Dieter — Sat, 02 Aug 2008 10:31:17 +0000

With MyISAM one could easily copy a database directory from one server to another and there it could be used immidialety.

Will this work with a InnoDB database that has been splitted to files too?

By: guzik » Blog Archive » MySQL: multiple tablespaces

guzik » Blog Archive » MySQL: multiple tablespaces — Sat, 02 Aug 2008 03:09:34 +0000

[...] Differences Between innodb_data_file_path and innodb_file_per_table [...]

By: phasnox

phasnox — Wed, 02 Jul 2008 17:15:13 +0000

Hi, great article..
you said
“You can specify multiple file paths using multiple innodb_file_per_table options in my.cnf, and ?spread the load? over multiple partitions or hard drives. ”

how do you do that?

By: Xaprb

Xaprb — Sun, 22 Jun 2008 12:34:23 +0000

With file-per-table, the shared tablespace is still configurable as usual. It just doesn’t have as much data in it, so you can configure it to be smaller. It does have more than meta-data, though. For example: undo logs, insert buffer, doublewrite buffer, etc. Lots of “real” data — the kind of stuff that will cause lost data if you delete it.

By: Gavin Towey

Gavin Towey — Fri, 20 Jun 2008 21:14:45 +0000

You don’t even have to do that much to convert tables from the single tablespace to the individual files. After enabling “innodb_file_per_table” and restarting mysql just do “ALTER TABLE foo ENGINE=InnoDB” and it will rebuild the table and pull it out of the shared tablespace.

However if you ever want to reclaim all that shared tablespace then you’ll have to dump the db, shutdown mysql & delete the tablespace / log & .frm files then edit the my.cnf to re-adjust the shared tablespace file sizes and then restart and let mysql build empty files, then import your data back in.

It’s also been shown that the shared tablespace has a bit faster read/write performance.

By: Morgan Tocker

Morgan Tocker — Fri, 20 Jun 2008 19:06:16 +0000

There’s situations when either one can be a better choice.

There are more disadvantages of using file per table – you end up consuming significantly more file descriptors (which is a problem particularly for MySQL on Windows). The main InnoDB thread that wakes up every few seconds will also have to flush a lot more files when it checkpoints.

You don’t need to mysqldump the data to convert from the shared global tablespace to the file per table model (but you don’t reclaim space unless you do). A CREATE TABLE new_table LIKE old_table; INSERT INTO new_table SELECT * FROM old_table; DROP TABLE old_table; RENAME TABLE new_table to old_table; is the alternative.