A virtual-machine or other disk-image file can have a large logical length while occupying much less physical storage. Sparse regions represent stretches of zero bytes without allocating ordinary blocks for all of them. A transfer that expands those regions can need substantially more destination space.

Measure the two sizes

Shut down or export the owning application using its documented procedure before copying the image. A file that is still changing creates a separate consistency problem that sparse-file handling does not solve.

Use GNU du with a summary and human-readable output on the quoted image path to inspect allocated usage. Compare that with du using --apparent-size for the same file. Record both values and confirm that they refer to the image itself rather than the folder containing several images.

A large difference is a reason to examine the copy method and destination. It does not mean the image is corrupt or that its unused logical regions can be deleted from the file manually. The image format and its owning application still define how its contents are interpreted.

Test the actual transfer route

GNU cp documents sparse handling that can attempt to preserve or create holes in regular destination files. Other tools, archives, network services and filesystems may behave differently. Do not assume that the receiving storage needs only the source's currently allocated space because the filename is unchanged.

For an important image, establish enough destination capacity and use a documented copy or export route that supports the required representation. Check the resulting apparent size and allocated usage at the destination; a successful transfer can legitimately use a different allocation amount.

Verify content integrity where appropriate, then test the copied image through its application without discarding the original. Ensure that any test which starts a copied virtual machine will not conflict with the original machine's identity or workload. Completion means the image is usable at the destination and its actual storage requirement is understood.

Sources: Ubuntu documentation, GNU documentation.