A storage system manages correspondence relationships between physical addresses and logical addresses inside a storage device, as well as logical spaces provided by a plurality of storage devices, and when a determination is made as to whether first data and second data are stored in the same storage device in a case in which the first data and the second data are exchanged inside a logical space, and the determination is found to be affirmative, the storage device replaces the logical address corresponding to the first data with the logical address corresponding to the second data without changing the physical address of the physical area in which the first data is stored and the physical address of the physical area in which the second data is stored.

The management computer stores a configuration information of a storage, a configuration information of a host computer and a VM, an information on a service level of the VM, and a performance information of a storage subsystem and a network. If an access path that the host computer uses to access a volume is changed in response to a change of storage configuration, an I/O performance of the VM operating in the host computer may be changed. If the change of state of the storage is detected, the management computer calculates a change of state of whether a service level defined for the VM is satisfied, and selects an appropriate host computer in which the VM should be operated.

The storage system is capable of creating one or more virtual storage subsystems to which virtual resources having logically divided a processing capacity of the physical resources are allocated, and upon creating a virtual volume for receiving I/O requests from the host within the virtual storage subsystem, the virtual storage subsystem allocates the virtual resource to the virtual volume, and when an I/O request to the virtual volume is received from the host, performs processing related to the I/O request using the virtual resource having been allocated. According further to the storage system, after allocating the virtual resource to the virtual volume, the storage system raises a utilization rate of the virtual resource allocated to the virtual volume in a stepwise manner.

According to an embodiment, when a storage status of a first storage unit is recognized as a protected state, a control unit writes data to a second storage unit. When a read target address is recorded in a data migration log area, the control unit reads data from the second storage unit. When the read target address is not recorded in the data migration log area, the control unit reads data from the first storage unit.

The over-provisioning (OP) of a physical storage device (PSD) may be increased, and the useful life of the PSD increased, by converting uncompressed data stored on the PSD to compressed data. It may be determined that increasing the useful life of the PSD, and the data reduction resulting from the compression, outweigh the benefit of faster I/O response times if the data remains uncompressed. A first portion of the PSD may be initially reserved for compression. A second portion of the PSD may store compressed data. It may be determined whether it is desirable to increase the OP of the PSD to thereby reduce the effective write rate on the PSD. If compression is determined to be desirable, the dynamic portion may be compressed, thereby reducing the amount of storage space consumed by the data, and freeing up storage space that can be used by the PSD for OP.

A storage unit according to one aspect of the present invention comprises a storage controller and a plurality of storage devices. Each storage device has nonvolatile semiconductor memories serving as storage media. The controller of each storage device diagnoses the state of degradation of the nonvolatile semiconductor memories, and if one of the nonvolatile semiconductor memories is expected to be nearing end of life, then the controller copies the data stored in that degraded nonvolatile semiconductor memory to another nonvolatile semiconductor memory, and then performs shutdown processing for the degraded nonvolatile semiconductor memory, as well as storage capacity reduction processing.

Provided are a computer program product, system, and method for selective write control in accordance with the present description. In one aspect, a write operation which is associated with a read operation, may be selectively discarded if write operations have been disabled and if the write operation is directed to update a designated write operation acceptance area such as metadata associated with the target data set, for example. As a result, the read operation may be permitted to proceed and will not fail because the associated write operation was discarded rather than attempting to commit the write operation to the designated write operation acceptance area, thereby avoiding an error condition for a storage unit such as a volume, in which write operations have been disabled. Accordingly, applications which seek to perform read operations may be permitted to access data stored on such a volume. Other aspects are described.

A method of transparently inserting a virtual storage layer into a Fibre channel based storage area network (SAN) while maintaining continuous I/O operations is provided. A device is inserted between a host entity and a first storage device. The device identifies a plurality of first paths between the host entity and the first storage device, and defines a plurality of second paths by defining, for each first path among the plurality of first paths, a corresponding second path between the host entity and a second storage device. The device determines, for each of the plurality of first paths, a respective first state. The device establishes, for each of the second paths among the plurality of second paths, a second state based on the first state of the corresponding first path. The device redirects, to the second storage device, communications directed from the host entity to the first storage device, via the plurality of second paths.

Methods and systems for collision handling during an asynchronous replication are provided. A system includes a cache memory system comprising a number of cache memory pages. A collision detector detects when a host is attempting to overwrite a cache memory page that has not been completely replicated. A revision page tagger copies the cache memory page to a free page and tags the copied page as protected.

Some examples describe data locality solutions for a hyperconverged computing system. In an example, a data request may be received at a Virtual Storage Appliance (VSA) node amongst a plurality of VSA nodes in a hyperconverged computing system. A determination may be made whether a remapped logical block address (LBA) associated with the data request is included on a first mapping layer on the VSA node. In response to a determination that the remapped LBA associated with the data request is present on the first mapping layer of the VSA node, the remapped LBA may be used to resolve the data request. In response to a determination that the remapped LBA associated with another data request is not present on the first mapping layer of the VSA node, a second mapping layer on the VSA node may be used to resolve the other data request.