taring vmdk files does not preserve thinness

Jakub Žitný asked:

we have NFS storage, where we store our backups.. we manipulate with them from linux machine where the nfs is also mounted..
So, for example thin provisioned thin.vmdk disk is on linux seen as thin.vmdk and thin-flat.vmdk. We want to archive and compress them with tar and gzip, however when issuing simple tar command on those two.. the thin just dissappears and everythnig is suddenly 10G.

Even when I try to tar the thin-flat.vmdk, which has 1.6G, separately (with “tar cf thin.tar thin-flat.vmdk”) it makes 10G tar file. This also happened when the I tried to run tar cf /extfs/thin.tar to create the tar on ext fs.

What kind of sorcery is this? Does anybody have a clue?

Thanks a lot.

My answer:

From the GNU tar(1) man page:

       -S, --sparse
              handle sparse files efficiently

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