1. A method for migrating a first virtual disk from a first flexible volume to a second flexible volume on a storage system having a processor and a memory, comprising: creating a second virtual disk on the second flexible volume; initiating a copy process to copy data from the first virtual disk to the second virtual disk; receiving a data access request directed to the data being copied from the first virtual disk to the second virtual disk; in response to the data access request, that is directed to the data being copied, being a read request, reading the data from the first virtual disk; and in response to the data access request, that is directed to the data being copied, being a write request, creating a copy of the write request, issuing the write request to the first virtual disk, issuing the copied write request to the second virtual disk, and determining whether the write request at the first virtual disk and the copied write request at the second virtual disk succeed, copying new data associated with the write request from the virtual disk to the second virtual disk in response to determining that the write request and the copied write request did not succeed.