Methods and systems for managing I/O requests to minimize disruption required for data encapsulation and de-encapsulation

1. A method comprising:

enabling evaluation of encapsulation of a physical volume by a virtualization layer that presents a virtual volume before committing to the virtual volume, wherein the virtual volume comprises a logical representation of the physical volume, the enabling comprising:

providing the virtualization layer comprising a SCSI virtualization layer configured to present the virtual volume to a host, a volume virtualization layer configured to generate the virtual volume, and a back-end services layer configured to import the physical volume;

preventing access to the physical volume through the virtualization layer before presenting the virtual volume to a host; and

preventing the virtualization layer from moving data on the physical volume before committing to the virtual volume.

2. The method of claim 1 wherein preventing access to the physical volume through the virtual volume comprises setting an attribute in the virtualization layer to a protection value.

3. The method of claim 1 further comprising checking that the virtual volume comprises a one-to-one logical representation of the physical volume.

4. The method of claim 1 further comprising, after committing to the virtual volume, changing an attribute associated with the virtualization layer from a test value to a normal value.

5. The method of claim 1 further comprising, after enabling evaluation of the encapsulation, continuing to prevent direct access to the physical volume until after eliminating a direct presentation to the host of the physical volume.

6. The method of claim 1 wherein the virtualization layer further comprises a switch, metadata storage and a storage processor to control the switch using data in the metadata storage.

7. A method for enabling evaluation of a physical volume used as data storage for a virtualization layer before committing to direct access to the physical volume, wherein the virtualization layer comprises a logical representation of the physical volume, the method comprising:

providing the virtualization layer further comprising a SCSI virtualization layer configured to present the virtual volume to a host, a volume virtualization layer configured to generate the virtual volume, and a back-end services layer configured to import the physical volume;

preventing direct access to the physical volume before presenting the physical volume directly to a host; and

preventing the virtualization layer from moving data on the physical volume while redirecting to the physical volume a first plurality of I/O requests that were directed to the virtualization layer.

8. The method of claim 7 wherein the virtualization layer further comprises a switch, metadata storage and a storage processor to control the switch using data in the metadata storage.

9. The method of claim 7 wherein preventing direct access to the physical volume comprises setting an attribute in a filter driver associated with an inherent identifier of the physical volume to a protection value.

10. The method of claim 7 further comprising, prior to redirecting the first plurality of I/O requests, checking that a virtual volume comprises a one-to-one logical representation of the physical volume and setting an attribute in the virtualization layer to a test value that prevents the virtualization layer from moving data on the physical volume.

11. The method of claim 7 further comprising resuming access to the physical volume via a virtual volume by:

terminating the redirection of I/O requests that were directed to the virtual volume and the redirection of I/O requests that were directed to the physical volume;

enabling I/O requests that were directed to the virtual volume to access the virtual volume; and

preventing I/O requests that were directed to the physical volume from accessing the physical volume.