I have a Drobo (gen 2) directly attached via FireWire to an iMac running Yosemite. There are a number of files and folders that I would like to delete permanently. In other words, I don't want those files or folders to be in any way recoverable. I do have backups, but a full reformatting of the drives really is not practical/desireable. Would the "Secure Empty Trash" option on OS X be the best alternate? Please advise on the best way to handle this task. Thanks!