US 7721282

Here's a concise summary of US patent 7721282:

Patent Number: US7721282B1

Title: Block-level I/O subsystem for distributed application environment management

Current Assignee: Intellectual Ventures II LLC (as of 2023-11-06)
Originally assigned to Panta Systems Inc.

Inventors: Pradip Kulkarni, Mukul Kumar, Adhir Potdar, Richard Au, James M. Mott, Tung M. Nguyen

Filing Date: March 30, 2006

Issue Date: May 18, 2010

Abstract: An embodiment of the present invention is directed to a system for distributing an application environment to a compute node. The system includes a first storage unit for storing blocks of a root image of the compute node and a second storage unit for storing a leaf image comprising new data blocks and changes to the blocks of the root image. The system further includes a union block device for interfacing between the compute node and the first and second storage units to distribute the application environment to the compute node. The union block device creates the application environment by merging the blocks of the root image stored on the first storage unit with the leaf image stored on the second storage unit.

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Plain-Language Overview of Independent Claims:

Claim 1 (System Claim):
This claim describes a system for providing an application environment to a computer. It involves:

• A compute node (a computer system).
• A first storage unit (non-volatile memory) that holds "blocks" of a "root image." This root image is a computer program, and a file within it consists of at least one block of data.
• A second storage unit (non-volatile memory) that stores a "leaf image." This leaf image contains new data blocks and any changes made to the blocks originally in the root image.
• A union block device (UBD), which is a driver. This UBD acts as an intermediary between the compute node and both storage units. Its role is to combine the blocks from the root image and the leaf image to create the complete application environment for the compute node. Crucially, when the compute node wants to write data (a "sector X"), the UBD first sets up a persistent mapping for that sector and then writes the data to the second storage unit (where the leaf image is stored). The UBD is a "low-level driver" that operates between the storage units and the compute node's file system.

Claim 15 (Method Claim):
This claim outlines a method for distributing an application environment to a compute node. It includes the following steps:

• Storing blocks of a root image (a computer program, with files made of blocks of data) for a compute node on a first non-volatile storage unit.
• Storing a leaf image (containing new data and changes to the root image blocks) on a second non-volatile storage unit.
• Merging the blocks from the root image and the leaf image to create the application environment. This merging process happens at a low operational level, between the storage units and the compute node's file system.
• Delivering the resulting application environment to the compute node.
• The method also includes modifying the leaf image when the compute node interacts with its application environment. This modification specifically describes that upon receiving a write request from the compute node for a "sector X," the method involves creating a persistent mapping for that sector and then writing the sector to the second storage unit.

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Litigation Information (as of April 26, 2026):
The patent US7721282B1 is currently involved in litigation, with several cases filed in various US District Courts in Texas, including the Northern District Court (cases 3:25-cv-00632, 3:25-cv-02885, 3:25-cv-00631) and the Western District Court (cases 7:24-cv-00277, 1:25-cv-01147), and the Eastern District Court (case 4:25-cv-00576).
Additionally, a PTAB case (IPR2026-00043) was filed, which was not instituted due to procedural reasons.