Deleting A Logical Drive To Increase Raid 0/1 Space - HP Surestore Disk Array 12h - And FC60 Service Manual

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.
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