Patent ID: 7480780
Filing Date: 2009-01-20
Classification: G06F

Abstract:
1. An information system comprising: a host; a primary storage system connected to said host, said primary storage system including a primary disk controller and a plurality of first disks for storing data; at least one external storage system, each having an external disk controller and a plurality of second disks for storing data, said second disks being configured in a redundant configuration to provide protection against data loss in the event of failure of one or more of the second disks, wherein said primary storage system uses virtual devices to treat logical devices in said at least one external storage system as if they are logical devices in said primary storage system; a first logical device formed in said at least one external storage system from the plurality of said second disks, said first logical device being used by said primary storage system to create a first virtual device in the primary storage system; and a network which interconnects said primary storage system, and said at least one external storage system to each other, wherein the primary storage system periodically checks I/O performance of the at least one external storage system by periodically accessing the first logical device that is used by said primary storage system for the first virtual device, wherein the primary storage system assumes that one of said plurality of second disks that forms a part of the first logical device in said at least one external storage system has failed when the I/O performance has decreased by a predetermined amount, wherein, when said primary storage system assumes that one of the plurality of second disks that forms a part of the first logical device has failed, said primary storage system automatically migrates data from the first logical device of said at least one external storage system to a second logical device in said primary storage system to avoid data loss by locating an unused second logical device, stopping processing of any input/output (I/O) operations from the host, reallocating a port and logical unit number to the second logical device, copying data from the virtual device to the second logical device, and resuming processing of I/O operations from the host without waiting for the copying of data to be completed, wherein said primary storage system is configured to periodically access the first logical device in the external storage system to determine whether a throughput in response to an access request has decreased, and wherein said throughput of the external storage system is measured by read performance in response to the access request that decreases by said predetermined amount based on a need of the external storage system to reconstruct read data using parity information to retrieve the read data.