HP Surestore Disk Array FC60 HP SureStore E Disk Array 12H User's and Service - Page 97

Concepts and Management Disk Array Hardware Figure 23. Installing a Second High-Capacity Disk Disk Stamps Because data is distributed across all disks, the array controller must keep track of which disks are installed in the array. To do this, the array controller writes a unique stamp on each disk. The disk stamp includes a unique number assigned to the disk (typically its serial number), and the numbers of the other disks in the disk set. This information allows the array controller to determine if any disk is missing from the disk set. The disk stamp identifies each disk's "logical" position in the array configuration relative to the other disks. When managing data, the array controller deals in terms of logical position, rather than physical location in the array enclosure. Thus, disks can be moved to different enclosure slots without any impact on array operation. As long as the correct disks are installed, the array controller is satisfied. When another disk is installed in the array enclosure, the array controller checks the disk stamp to determine if the disk is new or if it was previously installed in another array. In the latter case, the array controller assumes there may be some valuable data on the disk and does not include it (even automatically) until you tell it explicitly to do so. Once included, the disk is given a new stamp indicating it now belongs to the array's disk set. 97 Concepts