The Holey Copy-on-Write Device (HoleyCoW) is a distributed logical volume manager based on Xen blktap and aimed at cloud computing. It is motivated by the observation that virtual volumes stored in a common shared storage pool originate from multiple tenants and host a variety of application profiles. It provides two key features:

• Block-based deduplication, removing redundancy among unrelated volumes even when stored in different file system types.
• Writable snapshots and snapshot promotion, for database server scalability.

HoleyCoW is free software and welcomes your collaboration and feedback.