Disconnected Operation for Systems Utilizing Cloud Storage

• US 20150052392A1
• Filed: 08/19/2013
• Published: 02/19/2015
• Est. Priority Date: 08/19/2013
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Mickens, James W., Elson, Jeremy E., Nightingale, Edmund B., Fan, Bin, Kadav, Asim, Khan, Osama
• Granted Patent: US 11,422,907 B2
• Time in Patent Office: Days
• US Class Current: 714/15
• CPC Class Codes: G06F 11/2069 Management of state, configuration or failover
• CPC Class Codes: G06F 11/2082 Data synchronisation
• CPC Class Codes: G06F 11/2087 with a common controller

Abstract

While connected to cloud storage, a computing device writes data and metadata to the cloud storage, indicates success of the write to an application of the computing device, and, after indicating success to the application, writes the data and metadata to local storage of the computing device. The data and metadata may be written to different areas of the local storage. The computing device may also determine that it has recovered from a crash or has connected to the cloud storage after operating disconnected and reconcile the local storage with the cloud storage. The reconciliation may be based at least on a comparison of the metadata stored in the area of the local storage with metadata received from the cloud storage. The cloud storage may store each item of data contiguously with its metadata as an expanded block.

Claims

1. A computer-implemented method comprising:

writing to local storage of a computing device, the writing mirroring a write to cloud storage and including writing data to a first area of the local storage and metadata for the data to a second area of the local storage;

determining that the computing device has recovered from a crash or has connected to the cloud storage after operating disconnected from the cloud storage; and

reconciling the local storage with the cloud storage based at least on a comparison of the metadata stored in the second area of the local storage with metadata received from the cloud storage.

2. The method of claim 1, wherein the writing is performed while the computing device is connected to the cloud storage and, subsequent to the writing but before the determining, the computing device crashes or becomes disconnected from the cloud storage.

3. The method of claim 2, wherein, while the computing device is disconnected from the cloud storage, the computing device reads from and writes to the local storage.

4. The method of claim 1, wherein the determining comprises determining that the computing device has recovered from a crash and the reconciling comprises:

comparing version identifiers included in the metadata stored in the second area of the local storage with version identifiers included in the metadata received from the cloud storage, and

when the comparing indicates that the cloud storage has a more recent version of the data than the local storage, updating the local storage with the data from the cloud storage.

5. The method of claim 4, further comprising, while the computing device is connected to the cloud storage, writing the data to the first area of the local storage before writing the metadata to the second area of the local storage.

6. The method of claim 1, wherein the determining comprises determining that the computing device has connected to the cloud storage after operating disconnected from the cloud storage and the reconciling comprises:

comparing version identifiers included in the metadata stored in the second area of the local storage with version identifiers included in the metadata received from the cloud storage, and

when the comparison indicates that the local storage has a more recent version of the data than the cloud storage, updating the cloud storage with the data from the local storage.

7. The method of claim 6, further comprising, while the computing device is disconnected from the cloud storage, writing metadata to the second area of the local storage before writing data to the first area of local storage.

8. The method of claim 1, wherein the determining comprises determining that the computing device has connected to the cloud storage after both operating disconnected from the cloud storage and crashing while operating disconnected, and the reconciling comprises:

scanning the local storage to detect torn writes, the detecting being based at least on calculating checksums,

repairing the torn writes,

comparing version identifiers included in the metadata stored in the first area of the local storage with version identifiers included in the metadata received from the cloud storage, and

when the comparison indicates that the local storage has a more recent version of the data than the cloud storage, updating the cloud storage with the data from the local storage.

9. The method of claim 1, wherein the metadata stored in the second area of the local storage and the metadata received from the cloud storage include version identifiers.

10. One or more computer storage devices having stored thereon computer-executable instructions configured to program a computing device to perform operations comprising:

receiving a write request from an application of the computing device;

writing data specified by the write request to cloud storage;

indicating success of the write request to the application; and

after indicating success to the application, writing the data to local storage of the computing device.

11. The one or more computer storage devices of claim 10, the operations further comprising, prior to writing the data to the cloud storage, determining that the computing device is connected to the cloud storage.

12. The one or more computer storage devices of claim 10, the operations further comprising:

determining that the computing device is not connected to the cloud storage; and

while not connected to the cloud storage,

receiving a second write request, and

writing second data and metadata for the second data to the local storage, the writing the second data and metadata including writing the metadata to a first area of the local storage and, upon completion of writing the metadata, writing the second data to a second area of the local storage.

13. The one or more computer storage devices of claim 10, the operations further comprising reading from the cloud storage when the computing device is connected to the cloud storage and reading from the local storage when the computing device is not connected to the cloud storage.

14. The one or more computer storage devices of claim 10, wherein the writing includes writing the data to a first area of the local storage and, upon completing the writing of the data, writing metadata for the data to a second area of the local storage.

15. The one or more computer storage devices of claim 10, the operations further comprising incrementing a version identifier associated with the data,

wherein writing the data to the cloud storage includes writing the incremented version identifier as metadata for the data to the cloud storage, and

wherein writing the data to the local storage includes writing the incremented version identifier as metadata for the data to the local storage.

16. A system comprising:

a cloud storage device having a first processor and first one or more modules that, when operated by the first processor, receive writes including data items and metadata for the data items and store each data item contiguously with its metadata as an expanded block; and

a client device having a second processor and second one or more modules that, when operated by the second processor, write the data items and metadata to the cloud storage device and store the data items and metadata in local storage of the client device, wherein the data items are stored in a first area of the local storage and the metadata is stored in a second area of the local storage.

17. The system of claim 16, wherein the client device further includes a memory bitmap and the client device utilizes the memory bitmap to track writes to the local storage while the client device is disconnected from the cloud storage device.

18. The system of claim 16, wherein the second one or more modules include a virtual disk driver and a cloud client.

19. The system of claim 18, wherein the virtual disk driver receives write requests from applications of the client device and provides those write requests to the cloud client.

20. The system of claim 18, wherein the cloud client receives write requests from the virtual disk driver and performs the writing of the data items and metadata to the cloud storage device and the storing of the data items and metadata in the local storage.