Yes, it is possible to erasure files and folders in SAN storage, as long as Blancco File can access the file structure on the SAN from the host PC or server where Blancco File is installed.

Related articles:

http://support.blancco.com/index.php?/Knowledgebase/Article/View/592/62/how-can-i-use-blancco-file-to-securely-erase-files-and-folders-from-my-corporate-it-infrastructure