Patent ID: 8090907
Filing Date: 2012-01-03
Classification: G06F

Abstract:
1. A system for servicing an I/O request from a host device while transferring SRC (Synchronous Peer to Peer Remote Copy) from a backend storage subsystem to a storage virtualization appliance, the SRC including a primary storage device at a primary site and a secondary storage device at a secondary site, the system comprising: the storage virtualization appliance for receiving an I/O request from a host device, the I/O request being directed to the primary storage device or the secondary storage device; the storage virtualization appliance for appending a cache operation tag on the I/O request, the cache operation tag indicating one of: a read-write mode indicating the I/O request is completed by a cache memory and the I/O request is sent to the backend storage subsystem later, a no-flush mode indicating the I/O request is completed by a cache memory and the I/O request is not sent to the backend storage subsystems until the no-flush mode is turned off, and a write-through mode indicating the I/O request is forwarded to the backend storage subsystem by a cache memory and the I/O request is completed by the backend storage subsystem; a primary cache memory, at the primary site, for receiving and storing the I/O request with the cache operation tag from the I/O tag appending means and operating according to one of: the read-write mode, the no-flush mode, and the write-through mode; and a secondary cache memory, at a secondary site, for receiving and storing the I/O request with the cache operation tag from the I/O tag appending means and for operating according to one of two modes, the two modes comprising: the read-write mode and the no-flush mode, while transferring the SRC from the backend storage subsystem to the storage virtualization appliance, the primary cache memory and the secondary cache memory prevent any new I/O request from being submitted to the backend storage subsystem, wherein data consistency is maintained between the primary site and the secondary site with no interruption in servicing the I/O request issued from the host device, while transferring the SRC from the backend storage subsystem to the storage virtualization appliance, wherein the backend storage subsystem includes the primary storage device and the secondary storage device.