HP Surestore Disk Array FC60 HP SureStore E Disk Array 12H User's and Service - Page 96

Concepts and Management Disk Array Hardware Using Disks of Different Capacities Disks of different capacities can be installed in the same array, providing maximum flexibility and expandability for your disk array. This makes it easy to increase your array's data capacity as new, highercapacity disks become available. There is an important point to remember when using disks of different capacities in the same array: You should add at least two high-capacity disks to the array to use their entire capacity. If you add a single highcapacity disk, the array will not be able to use its full capacity. In this situation, the array can only use capacity equal to that of the largest disk already installed in the array. For example, if your disk array has only 4.3-Gigabyte disks and you add a single 9.1-Gigabyte disk, the array can only use 4.3 Gigabytes of the high-capacity disk (at least until another 9.1-Gigabyte disk is added). Figure 22. Using Disks of Different Capacities This is a result of the way in which redundant data is stored using RAID technology. Because there is no corresponding space on another disk for redundant data, the array cannot use the upper portion of the highcapacity disk. Thus, adding a single high-capacity disk will not yield all the additional capacity you had expected. To avoid this situation, always install at least two high capacity disks in the array. 96 Concepts