glandium/vmfs-tools — Issue #2: Handling of sparse files
Author: gabbe
Created: 2011-10-24 08:49:16+00:00
State: open

Since my .vmdk-files where created with thin provisioning, they are stored as sparse files. When I try to use tar with the --sparse option on a filesystem mounted with vmfs-fuse, the compression is impressive - but not realistic. A 100Gb virtual disk (containing about 2.2 Gb data) resulted in a tar file of 10240 bytes, and that is without gzip compression...
I now realize that "du" reports that the files uses 0 bytes on disk. If I use tar without the "--sparse" option, tar works fine but takes a very long time since it has to read the whole 100Gb and compress it to reduce the size of all those zeros.
Is this a known problem?

I am using vmfs-tools 0.2.1-1 on a ubuntu 11.10 rescue remix.