Oracle VM: Deleting VM Guest Image Files Does Not Release Space From Storage Repository If Sparse Allocation Mode
(Doc ID 2430219.1)
Last updated on FEBRUARY 03, 2019
Applies to:Oracle Cloud Infrastructure - Version N/A and later
Oracle VM - Version 3.2.7 to 3.4.5 [Release OVM32 to OVM34]
One would expect that creating a 100Gb file would occupy 100Gb of actual space in a storage pool. One would also expect that the free space for the pool would be reduced 100Gb as well. All this works as expected so creating a 100Gb VM image does reduce the free space in the storage pool by 100Gb.
If the storage pool has sparse mode enabled, storage space is not actually consumed until that disk space has non-zero data written to it. For example, a 100Gb file is created and an application writes exactly one disk block at the very end of the file. All intermediate space between the beginning of the file and that data at the end of the file is never written at all. On a sparse-mode storage repository that file would occupy exactly one disk block, not enough disk blocks for a 100Gb file.
On traditional storage, deleting that 100Gb disk file returns 100Gb to the storage free space but if sparse mode is enabled it does not.
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