Patent ID: 11941255
Assignee: HITACHI, LTD.
Field: Computer technology (Electrical engineering)
Classification: CPC G | IPC G

Claim 0:
1. A storage system comprising
a plurality of first storage devices, and
a control unit coupled to the plurality of first storage devices, wherein
the control unit is configured to:
form a pool area, which comprises a plurality of virtual parity groups, based on a storage area of the plurality of first storage devices,
manage a mapping which comprises associations between the plurality of virtual parity groups and the plurality of first storage devices,
store, when storing a first data set in a first virtual parity group, the first data set in the plurality of first storage devices associated with the first virtual parity group,

wherein
the first data set comprises a plurality of first data elements whose number is a predetermined number, and
the first data elements are a plurality pieces of data and one or more pieces of redundant data and are respectively stored in different multiple storage devices, and

when a set of second storage devices is added,
form an additional pool area, which comprises an additional virtual parity group, based on the added set of second storage devices,
migrate at least one data element of the first data set of the first virtual parity group to the added set of second storage devices and not migrate at least one other data element of the first data set to the added set of second storage devices, and
change a part of associations for the first data set in order to associate a part of the first virtual parity group with a part of the added set of second storage devices instead of a part of the first storage devices, and maintain another part of the associations of the first virtual parity group with the first storage devices.