diff options
Diffstat (limited to 'qemu-options.hx')
| -rw-r--r-- | qemu-options.hx | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/qemu-options.hx b/qemu-options.hx index e26230bac5..7809036d8c 100644 --- a/qemu-options.hx +++ b/qemu-options.hx @@ -1457,9 +1457,13 @@ SRST (on/off; default: off) ``discard-no-unref`` - When enabled, discards from the guest will not cause cluster - allocations to be relinquished. This prevents qcow2 fragmentation - that would be caused by such discards. Besides potential + When enabled, data clusters will remain preallocated when they are + no longer used, e.g. because they are discarded or converted to + zero clusters. As usual, whether the old data is discarded or kept + on the protocol level (i.e. in the image file) depends on the + setting of the pass-discard-request option. Keeping the clusters + preallocated prevents qcow2 fragmentation that would otherwise be + caused by freeing and re-allocating them later. Besides potential performance degradation, such fragmentation can lead to increased allocation of clusters past the end of the image file, resulting in image files whose file length can grow much larger |