The Zumastor open source project provides enterprise storage features
for Linux NFS and CIFS file serving applications.  Based on ddsnap, a
filesystem independent virtual block device, Zumastor supports a broad
range of Linux host filesystems and provides them all with multiple
volume snapshots, multilevel remote replication and a command level
management interface.  Work to date has focussed primarily on stable
operation under full load, while tolerating multiple system failures. As
part of this work, the Linux block IO subsystem was improved to
eliminate deadlock issues that have traditionally plagued storage
subsystems, including ddsnap.  Ongoing work focusses on two main areas:
1) optimizing write throughput to snapshotted volumes and 2) improving
flexibility, stability and features of Linux volume management in order
to add provisioning capabilities to Linux that have become popular on
other operating systems.