Traditional Linux storage is built using several block layers and adding a file system on top. You can construct a block device out of a file system using the loop driver, but that interface loses some key functionality present in the block layer, most importantly the DAX interfaces.

As an alternative, we can squash some of the the loop driver functionality into a file system and present both file system interfaces as well as block device interfaces from the same driver.

This provides a uniform storage management interface where a single 'wholesale' file system aggregates a set of the available storage into a single logical store which can then be arbitrarily dis-aggregated into individual storage volumes which can then be used as traditional block devices for 'retail' file systems within the host OS or passed to virtual machines for storage in that environment.

This technique is being used within The Machine, a project within Hewlett Packard Enterprise, to provide convenient management of a pool of fabric attached memory shared among many Linux instances.

The presentation will show how the wholesale file system is managed and how the block layer is exported from it. Additional details about how storage locality is controlled using extended attributes will be included.