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MySQL 6.0 Reference Manual :: 13 Storage Engines :: 13.6 The InnoDB Storage Engine :: 13.6.3 InnoDB Configuration :: 13.6.3.2 Using Raw Devices for the Shared Tablespace
13.6.4 InnoDB Startup Options and System Variables »
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13.6.3.2. Using Raw Devices for the Shared Tablespace

You can use raw disk partitions as data files in the shared tablespace. By using a raw disk, you can perform non-buffered I/O on Windows and on some Unix systems without filesystem overhead, which may improve performance.

When you create a new data file, you must put the keyword newraw immediately after the data file size in innodb_data_file_path. The partition must be at least as large as the size that you specify. Note that 1MB in InnoDB is 1024 × 1024 bytes, whereas 1MB in disk specifications usually means 1,000,000 bytes. 

[mysqld]
innodb_data_home_dir=
innodb_data_file_path=/dev/hdd1:3Gnewraw;/dev/hdd2:2Gnewraw

The next time you start the server, InnoDB notices the newraw keyword and initializes the new partition. However, do not create or change any InnoDB tables yet. Otherwise, when you next restart the server, InnoDB reinitializes the partition and your changes are lost. (As a safety measure InnoDB prevents users from modifying data when any partition with newraw is specified.)

After InnoDB has initialized the new partition, stop the server, change newraw in the data file specification to raw: 

[mysqld]
innodb_data_home_dir=
innodb_data_file_path=/dev/hdd1:5Graw;/dev/hdd2:2Graw

Then restart the server and InnoDB allows changes to be made.

On Windows, you can allocate a disk partition as a data file like this: 

[mysqld]
innodb_data_home_dir=
innodb_data_file_path=//./D::10Gnewraw

The //./ corresponds to the Windows syntax of \\.\ for accessing physical drives.

When you use raw disk partitions, be sure that they have permissions that allow read and write access by the account used for running the MySQL server.


User Comments

Posted by M Z on August 26 2004 11:33am[Delete] [Edit]

The following does not work on Windows
innodb_data_home_dir=
innodb_data_file_path=//./D::10Gnewraw
I think the problem is in "::".

Posted by Andrew Button on July 19 2006 8:05am[Delete] [Edit]

This is how I set up MySQL to use a raw device on RedHat Linux ES4. I could not access the disk partiton directly so I had to create raw devices that link to the disk partitions.

Using parted I created the raw partition (it did not let me add it in the install as there is no mount point).

Assign this partition to a raw device using raw. I.e.

raw /dev/raw/raw1 /dev/cciss/c0d0p5

Then make accessible the raw device to mysql (as mentioned in the docs):

chown mysql dev/raw/raw1

Then use the raw device (as shown in the docs). i.e.

innodb_data_home_dir =
innodb_data_file_path = /dev/raw/raw1:20000Mnewraw;

Posted by Ralf Schwedler on August 16 2007 11:39am[Delete] [Edit]

Chowning the raw device like in

chown mysql /dev/raw/raw1

will fail after the next reboot, if the /dev-tree is dynamically created by, e.g. udev, a MAKEDEV-script or similar. After reboot, the device will regain its former permission, typically excluding access by mysql.

A permanent solution is (in the case of a udev-generated /dev) to create the file /etc/udev/rules.d/41-local-permissions-rules containing the single line:

KERNEL=="sda5" GROUP="mysql"

to make /dev/sda5 accessible to group mysql.

Posted by Seva E on January 16 2008 7:13am[Delete] [Edit]

innodb_file_per_table must be set to 0 (default). If it's set (to 1), InnoDB table data files (.ibd) will be created in the datadir instead of in the raw device's shared tablespace even if innodb_data_home_dir is blank.

Not sure if this is a bug or a feature, but this is not what I expected. Tested with mysql-5.0.22-2.1 (RHEL 5).

Posted by Joaquín Alcañiz on April 15 2008 7:32am[Delete] [Edit]

It works fine on Windows. Follow next steps:
1. Select a primary clear partition and format it on FAT32 (instead NTFS). Assign a drive letter to it, and compute its size in Mb or Gb (asume M: and 30Gb in this example)
2. Edit "my.ini" file and add on it:
innodb_data_home_dir=
innodb_data_file_path=//./M::30Gnewraw (yes, use "::")
3. Start mysqld service and WAIT until disk ends working. (see at LED on front your PC).
4. Stop mysqld service.
5. Edit "my.ini" file and change ("newraw" to "raw"):
innodb_data_file_path=//./M::30Graw
6. Start mysqld service again, you can create and load your databases.

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