Storage control apparatus and storage system comprising multiple storage control apparatuses

Abstract

A storage system has multiple disk controller (DKC) units that are coupled to one another in accordance with a coupling mode that satisfies the following (a1) through (a3): (a1) One DKC inside one DKC unit and one DKC inside another DKC unit are coupled via a second type of coupling medium that differs from the internal bus of the DKC and has a longer maximum communication distance than a first type of coupling medium, which is the same type of coupling medium as the internal bus of the DKC; (a2) the one DKC unit virtualizes a logical volume of the other DKC unit and provides this virtualized logical volume to host(s) coupled to the one DKC unit; and (a3) the other DKC unit virtualizes a logical volume of the DKC unit and provides this virtualized logical volume to host(s) coupled to the other DKC unit.

1 . A storage system coupled to a host computer, the storage system comprising:
 a plurality of storage units, each of storage units is including a controller and a storage medium,   wherein the plurality of storage units are recognized as one storage unit by the host computer, and   wherein a load of each of the storage units in the storage system is distributed by referring to a difference of I/O processing efficiency among the plurality of storage unit.   
     
     
         2 . The storage system according to  claim 1 ,
 wherein a process of distributing the load for a particular storage unit is performed by migrating a volume from the particular storage unit to a destination storage unit.   
     
     
         3 . The storage system according to  claim 2 ,
 wherein the difference of I/O processing efficiency is based on the difference between the I/O processing efficiency of the particular storage unit and the I/O processing efficiency of the destination storage unit.   
     
     
         4 . The storage system according to  claim 3 ,
 wherein the process of distributing the load is further performed by referring to a threshold information which is stored in a particular storage medium of the particular storage unit and which indicates to migrate the volume to the another storage unit.   
     
     
         5 . The storage system according to  claim 4 ,
 wherein the I/O processing efficiency is related to:   a distance between the particular storage unit and the destination storage unit,   a difference in capability between the particular storage unit and the destination storage unit,   a difference of type of the storage medium between the particular storage unit and the destination storage unit, or   a CPU load difference between the particular storage unit and the destination storage unit.   
     
     
         6 . A method for load distribution in a storage system which is coupled to a host computer and comprises a plurality of storage units, each of the storage units including a controller and a storage medium, the method comprising the steps of:
 providing the plurality of units to the host computer as a single storage unit; and   distributing a load of each of the storage units in the storage system by referring to a difference of I/O processing efficiency among the plurality of storage units.   
     
     
         7 . The method for load distribution of storage system according to  claim 6 ,
 wherein the step of distributing the load for a particular storage unit is performed by migrating a volume from the particular storage unit to a destination storage unit.   
     
     
         8 . The method for load distribution of storage system according to  claim 7 ,
 wherein the difference of I/O processing efficiency is based on the difference between the I/O processing efficiency of the particular storage unit and the I/O processing efficiency of the destination storage unit.   
     
     
         9 . The method for load distribution of storage system according to  claim 8 ,
 wherein the process of distributing the load is further performed by referring to a threshold information which is stored in a particular storage medium of the particular storage unit and which indicates to migrate the volume to the another storage unit.   
     
     
         10 . The method for load distribution of storage system according to  claim 9 ,
 wherein the I/O processing efficiency is related to:   a distance between the particular storage unit and the destination storage unit,   a difference in capability between the particular storage unit and the destination storage unit,   a difference of type of the storage medium between the particular storage unit and the destination storage unit, or   a CPU load difference between the particular storage unit and the destination storage unit.