Instead of forcing users to manually configure a block device to use
with devmapper, this gives the user the option to let the devmapper
driver configure a device for them.
Adds several new options to the devmapper storage-opts:
- dm.directlvm_device="" - path to the block device to configure for
direct-lvm
- dm.thinp_percent=95 - sets the percentage of space to use for
storage from the passed in block device
- dm.thinp_metapercent=1 - sets the percentage of space to for metadata
storage from the passed in block device
- dm.thinp_autoextend_threshold=80 - sets the threshold for when `lvm`
should automatically extend the thin pool as a percentage of the total
storage space
- dm.thinp_autoextend_percent=20 - sets the percentage to increase the
thin pool by when an autoextend is triggered.
Defaults are taken from
[here](https://docs.docker.com/engine/userguide/storagedriver/device-mapper-driver/#/configure-direct-lvm-mode-for-production)
The only option that is required is `dm.directlvm_device` for docker to
set everything up.
Changes to these settings are not currently supported and will error
out.
Future work could support allowing changes to these values.
Signed-off-by: Brian Goff <cpuguy83@gmail.com>
