HP Surestore Disk Array FC60 HP SureStore E Disk Array 12H User's and Service - Page 111

Concepts and Management Optimizing Performance Deleting a Logical Drive to Increase RAID 0/1 Space Unlike deleting files from the operating system level, deleting a logical drive does free up capacity for use as RAID 0/1 space. To understand how file space is allocated, you must differentiate between file system free space and free space (or unallocated capacity) within the disk array. The following example should help make this distinction clear. If you create a three-Gigabyte logical drive on the disk array and then write three Gigabytes of data to that logical drive, you have used three Gigabytes of space on the disk array. If you then "erase" the data by deleting all the files you have written, you now have no user data on the disk array, but the logical drive is still occupying three Gigabytes of space. Therefore, even if you delete files from the file system, updating the structures within the file system to indicate deletion is not the same as actually freeing space within the disk array. The file system data still occupies the same amount of space on the disk array, so deleting files from the file system will not release capacity back to the disk array for use as RAID 0/1 space. The key point is this: Once data has been written to the disk array, you cannot reclaim the space consumed by that data simply by deleting files from the operating system. To truly erase the data and reclaim the capacity for use as RAID 0/1 space, you must delete the logical drive on which the data resides. Of course this will erase all the data on that particular logical drive, so you must make sure you backup any critical data on a logical drive before you delete it. 111 Concepts