Patent ID: 8307159

Claim:
A storage system comprising: a storage array, the storage array including a storage drive pair, the storage drive pair including a first type storage device and a second type storage device, wherein the storage array is provided as a Redundant Array of Inexpensive Disks (RAID) configuration, the storage drive pair being a RAID drive pair; and a storage array controller, the storage array controller configured for being communicatively coupled with the storage array and a host server, the storage array controller being further configured for reading from the storage array and writing to the storage array based upon commands received from the host server, wherein the storage system is configured for copying a data set from the second type storage device to a spare first type storage device of the storage array during a first type storage device rebuild process and tracking a portion of the data set that has been copied to the spare first type storage device by keeping a pointer to a rebuild high water mark of the portion of the data set that has been copied to the spare first type storage device, the storage system being further configured for reading, prior to completion of copying of the data set from the second type storage device to the spare first type storage device, a subset of the data set from the spare first type storage device based upon a read command requesting said subset of the data set, said subset of the data set including a first amount of data, said data set including a second amount of data, said first amount of data being less than said second amount of data.