For example, Patent Literature 1 through Patent Literature 5 below are known.
Patent Literature 1 is an invention in which multiple disk control apparatuses share multiple disk apparatuses via a switch. The disk control apparatus load leveling is attempted in accordance with the disk control apparatus, which processes a read/write request to the disk apparatus, dynamically changing. In Patent Literature 1, a host computer recognizes one physical disk apparatus as one disk apparatus.
Patent Literature 2 is related to technology called virtual storage. In Patent Literature 2, a storage system has a virtual storage identifier and a real storage identifier. In Patent Literature 2, a virtual LUN and a real LUN exist with respect to a LUN (Logical Unit Number), which is a logical volume number specified when a server performs a read/write. The virtual LUN is unique inside a virtual storage, and the real LUN is unique inside a real storage. The virtual storage is configured in accordance with one or more real storages. For example, a single virtual storage is realized on the basis of multiple real storages. Furthermore, even when a real storage identifier changes in accordance with an old real storage being replaced by a new real storage, the handing over of the virtual storage identifier can make it appear to the virtual storage host that operations are continuing.
Patent Literature 3 discloses technology for real storage load leveling in accordance with copying a virtual LUN between real storages, which comprise a virtual storage.
Patent Literature 4 relates to technology called “capacity virtualization”. Capacity virtualization is also called thin provisioning. In Patent Literature 4, a virtual storage has a capacity virtualization function. In the capacity virtualization function, a relatively large-capacity storage area called a capacity pool is partitioned into segments called pages. Generally speaking, when a logical volume is defined, a logical volume capacity is specified in addition to the LUN, and a logical volume corresponding to this capacity is reserved in the storage. In a virtual storage that has a capacity virtualization function, a storage area is not reserved as a logical volume when the logical volume is defined, and in a case where a write actually occurs with respect to the logical volume, a page is allocated to a write-destination area in the logical volume. This makes it possible to reduce the storage area actually being used. Since the trigger for allocating the storage area is the occurrence of a write, an administrator may define a relatively large capacity as the logical volume capacity without having to compute the exact capacity of the logical volume, thereby also enabling management costs to be lowered.
In Patent Literature 5, a storage system A is coupled to an external storage system, and this external storage system is virtually made to appear as a storage capacity inside the storage system A. A capacity virtualization function (a function, which treats a storage capacity as a storage pool, partitions the storage capacity into page units, and allocates the page when there is a write request) is applied to the external storage system. The storage system A migrates to a storage system B a logical volume to which a page of the external storage system, which is also coupled to the storage system B, is allocated. In Patent Literature 5, even when a logical volume is migrated, storage system A comprises the storage pool of the external storage system, and storage system A also comprises the page allocation and release rights of the storage pool. A read/write with respect to the migrated logical volume is executed by the storage system B.
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