Data storage mirroring using virtual mirror

A controller for providing a virtual mirror of a primary storage device on a secondary storage device, said primary and secondary storage devices configured to be accessible for read/write operations through a file system, the controller being operable to:

• provide a virtual mirror application arranged between the storage devices and the file system, the virtual mirror application comprising a map for translating primary data storage locations on said primary storage device to secondary data storage locations on said secondary storage device;
• and
• utilise said map to enable data stored on said secondary storage device to mirror data stored on said primary storage device such that said secondary storage device appears to the file system as an exact copy of the primary storage device.

A controller for providing a virtual mirror of a primary storage device on a secondary storage device, said primary and secondary storage devices configured to be accessible for read/write operations through a file system, the controller utilising a virtual mirror application arranged between the storage devices and the file system such that said secondary storage device appears to the file system as an exact copy of the primary storage device and being operable to:

• define, using the virtual mirror application, a plurality of primary storage segments on a primary storage device, each primary storage segment having a primary index, to write data to at least one primary storage segment of the primary storage device, to determine, using the virtual mirror application, the primary segment index of the or each primary storage segment, to select, using the virtual mirror application, one or more available secondary storage segments on the secondary storage device, to store, using the virtual mirror application, the secondary index of the or each selected secondary storage segment against the primary segment index of the or each primary storage segment to which the data has been written to;
• and to write a copy of said data to the or each selected secondary storage segments.

A controller for reading data from a virtual mirror of a primary storage device on a secondary storage device, said primary and secondary storage devices configured to be accessible for read/write operations through a file system, the controller utilising a virtual mirror application arranged between the storage devices and the file system such that said secondary storage device appears to the file system as an exact copy of the primary storage device, the primary storage device having a plurality of primary storage segments defined thereon by the virtual mirror application, each primary storage segment having a primary index, the secondary storage device having a plurality of secondary storage segments defined thereon by the virtual mirror application, each secondary storage segment having a secondary segment index, the controller being operable to:

• determine, using the virtual mirror application, the primary index of the primary storage segment corresponding to said data, to determine the secondary index stored against said primary index;
• and to read said data from the secondary storage segment having said secondary index.