Abstract: A RAID disk array that is adaptable to host I/O traffic, wherein the RAID configuration is hidden from the host computer. The system dynamically determines the RAID configuration used to store host data to maximize response time performance and minimize the loss of disk space used for data protection. To maximize response time and avoid a write penalty, small write operations are mapped into RAID 1 configurations, and medium and large write operations are mapped into RAID 3 configurations. These segments are migrated into RAID 5 configurations as a background operation, to minimize the disk space lost. The system hides configuration changes necessary for the addition and/or deletion of disks to the disk array. While these changes are in progress, the disk array remains on-line and all host data is available for access and modification.