# Creating the application data thin pool

Use this procedure to create a thin pool for application data storage.

The following Control Center configuration variables are used to specify application data thin pools:

SERVICED_FS_TYPE
Default: devicemapper
The driver to manage application data storage on the serviced master host. Only devicemapper is supported in production deployments.
The only supported storage layout for the devicemapper driver is an LVM thin pool. To create a thin pool, use the serviced-storage utility. To specify the name of the thin pool device, use the SERVICED_DM_THINPOOLDEV variable.
SERVICED_DM_THINPOOLDEV
Default: (none)
The name of the thin pool device to use with the devicemapper storage driver.

Perform these steps:

1. Log in to the master host as root, or as a user with superuser privileges.
2. Create an LVM thin pool for application data.
To use an entire block device or partition for the thin pool, replace Device-Path with the device path:
serviced-storage create-thin-pool serviced Device-Path
To use 200GB of an LVM volume group for the thin pool, replace Volume-Group with the name of an LVM volume group:
serviced-storage create-thin-pool --size=200G serviced Volume-Group
On success, the result is the device mapper name of the thin pool, which always starts with /dev/mapper. Record the name for use in the next step.
3. Edit storage variables in the Control Center configuration file.
1. Open /etc/default/serviced in a text editor.
2. Locate the line for the SERVICED_FS_TYPE variable, and then make a copy of the line, immediately below the original.
3. Remove the number sign character (#) from the beginning of the line.
4. Locate the line for the SERVICED_DM_THINPOOLDEV variable, and then make a copy of the line, immediately below the original.
5. Remove the number sign character (#) from the beginning of the line.
6. Set the value to the device mapper name of the thin pool for application data.
7. Save the file, and then close the editor.
Proceed to the next chapter and configure the host.