BACKGROUND

This invention relates to a storage system.

Most storage systems have a power saving function for reducing power consumption. For example, in Patent Literature 1, there is disclosed a storage system configured to allow an administrator to apply power saving to a desired storage apparatus from a management apparatus. The storage system includes: a power saving instruction reception module configured to receive from a management console a power saving instruction for designating at least one storage apparatus included in a plurality of RAID groups, a plurality of logical units, and a plurality of physical storage apparatus; and a power saving control module configured to apply power saving to at least one physical storage apparatus corresponding to the storage apparatus designated by the power saving instruction.

Patent Literature 1: US 2008/0126702 A1

SUMMARY

Storage systems are constantly required to improve responsiveness. With the rising number of cases in which storage systems are built through use of flash drives, increasing importance has been placed on guarantee of responsiveness of the storage systems. Therefore, it is desired to provide a technology for improving responsiveness to a host under a power saving state of a storage system.

An aspect of this invention is a storage system, including: a redundancy group formed of a plurality of storage drives configured to store host data and redundant data in a distributed manner; and a controller configured to control access to the redundancy group. The controller being configured to: select, from among the plurality of storage drives in the redundancy group, a part of the plurality of storage drives in an upper limit number equal to or smaller than a redundancy level of the redundancy group, and set the part of the plurality of storage drives to a power saving state; receive, from a host, a read request with respect to a target storage drive included in the redundancy group; and restore, when the target storage drive is in the power saving state, target data corresponding to the read request from data collected from a part of the plurality of storage drives different from the target storage drive in the redundancy group, and return the target data to the host.

According to at least one aspect of this disclosure, it is possible to improve the responsiveness of the storage system during power saving.

