compress Long size file into multiple limited size xz file
Use split. 

Example: 
xz -e9vfc &lt; yourFile.vdi | split -b 1024m - yourFile.vdi.xz.

This will split yourFile.vdi into compressed chunks of 1GB, suffixed by aa-zz. 

To reassemble, do cat yourFile.vdi.xz.* &gt; yourFile.xz

7-zip is MORE capable, but less ubiquitous. You'll want to checksum your backups and verify it every once in a while. Have a look at a GUI package of p7zip. It will let you select compression levels and volume sizes of 1GB... If you're doing this in an unattended batchjob, p7zip is dirtier. I can find one of my snippets if you need it.

A nice thing about xz though, is that you can assign n cores to a job. I believe it's the -T flag. Remember to nice it to 20 if you intend to use that mac for something other than a big paperweight if you use all cores at once.