I created a snapshot of a large database today. I wanted to preserve a version of the database without doing full backup. Snapshots are based on sparse files. They contain only original database pages that have been modified since snapshot was taken.
However, I was shocked when I opened Windows Explorer and when I saw that size of snapshot files is identical to size of original data files. That would have huge implication on my server if it was true.
After I calmed down (and after I realized that our server is still working), I looked in BOL and then I've googled around. I've found that there is a difference between Size that Explorer is showing and Size on Disk. When I opened properties of a snapshot file I saw that Size of a particular file was a 14 GB while it occupied only 64 KB on disk.