Linux Symposium

File Systems: More Cooperation - Less Integration.

Alex Depoutovitch

Conventionally, file systems manage storage space available to user programs and provide it through the file interface. Information about the physical location of used and unused space is hidden from users. This makes the file system free space unavailable to other storage stack kernel components because of performance or layering violation reasons. This forces file systems architects to integrate additional functionality, like snapshotting and volume management, inside file systems increasing their complexity.

We propose a simple and easy to implement file system interface that allows different software components to efficiently share free storage space with a file system at a block level. We demonstrate the benefits of the new interface by optimizing an existing volume manager to store snapshot data in the file system free space, instead of requiring the space to be reserved in advance making it unavailable for other uses.

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