If the filesystem has been used for a while, there may be many "deleted" sectors which are not zeroed?
Some type of fsck (or nowadays possibly "trim") can zero all unused sectors of the image, before conversion?
If the filesystem has been used for a while, there may be many "deleted" sectors which are not zeroed?
Some type of fsck (or nowadays possibly "trim") can zero all unused sectors of the image, before conversion?