Some more information after experimenting with sparse images (both me and Michael).
After creating a .vhd image in a Vagrant guest, transferring it to a Windows machine while preserving its sparse nature proved to be not so straightforward. Samba, scp and rsync produce a regular 40GB file at the destination, not a sparse one. Probably the only chance is to use GNU tar or bsdtar on the guest to create a tar archive containing the sparse file, and use GNU tar to expand that on Windows, after transferring the archive (which is a regular file). That's just for a quick test: an official Vagrant image would need to be extracted by Vagrant on Windows, we still to figure out what it will do. Does anyone have any experience with backup software typically used on Windows, especially if they can backup and restore sparse files?
On OS X, the HFS+ filesystem has no support for sparse files, and Apple removed sparse file support from their implementation of UFS (which used to have them).
On 06/04/17 14:03, Laurentiu Pancescu wrote:
We should probably either:
- call GNU tar from Image Factory to preserve the sparseness of our
image files (and hope that Windows handles them properly)
- use VBoxManage to convert to .vhd (VirtualBox is not in our repos, but
Oracle offers a .rpm for EL7 systems).
I would prefer the second option, using VBoxManage to produce small non-sparse .VHD images for our Vagrant boxes, and avoid the compatibility problems posed by sparse files. But this would need to be done in Image Factory, so it's actually for Ian to decide if using VirtualBox is acceptable.