HP 127695-B21 Smart Array Controller Technology: Drive Array Expansion and Ext - Page 3
capacity expansion, The expansion process is entirely independent of the system OS. For example, if
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Smart Array Controller Technology: Drive Array Expansion and Extension capacity expansion Capacity expansion is the process of adding physical drives to an array that has already been configured. The logical drives (or volumes) that exist in the array before the expansion takes place are unchanged. Only the amount of free space in the array changes. For example, suppose that an existing array consisted of four physical drives and the administrator wants to expand the capacity to six physical drives. This is like having four glasses full of water, and pouring that water from the original four glasses into six glasses (see figure 1). The amount of water (the volume of the logical drive) has not changed - it has merely been redistributed, or expanded, into a larger number of containers (drives). figure 1. Array capacity expansion redistributes an array into a larger number of physical drives. The size of the logical drive does not change. Thus, if an existing array is nearly filled with logical drives, an administrator can add new physical drives and initiate a capacity expansion through ACU or ACU-XE. The program automatically checks the drive hardware configuration. Then, the existing logical drive is distributed across all physical drives in the expanded array without affecting any existing data. If the array being expanded contains more than one logical drive, data will be redistributed one logical drive at a time. The expansion process is entirely independent of the system OS. For example, if a 10-gigabyte (GB) logical volume is expanded from four drives into six drives, the OS is unaware of this change. The amount of time it takes to perform an online capacity expansion depends on several parameters: drive speed, the server microprocessor speed, the amount of other I/O work the server is doing, and the priority level of the capacity expansion. This priority level can be changed from low (the default in ACU) to medium or high to expand the volumes as quickly as possible. Depending on these factors, the expansion process takes somewhere between 10 - 15 minutes per GB. 3