By default, Docker puts data and metadata on a loop device backed by a sparse file. This is great from a usability point of view (zero configuration needed) but terrible from a performance point of view. To resolve this, real block devices should be provisioned for docker and docker needs to be configured to use direct-lvm storage driver.
To provision this, docker needs an unmounted storage space. Following commands lists the mounted devices,
df -aTh
The device can be unmounted using the following command where /dev/sdb is the storage required.
umount /dev/sdb
If any process is restricting it from being mounted you can check for other mountpoints and check for blocking processes by following commands
fuser /dev/sdb
lsof /dev/sdb
After unmounting you can give input or append in existing ansible install command as follows. This will format the /dev/sdb storage and provision it to be used with docker. Any data inside the partrition would be destroyed.
DirectLVMstorage=yes Docker_storage_devs=/dev/sdb
Docker daemon would also be configured by ansible script to use the specified volume as image and container storage.