.sfv is a text file that lists the crc32’s (hash) of the scene release rar files to verify if they are broken/modified in any way. They can sometimes have ascii art in them, or vague info on what topsite the release last went through, but thats rather rare these days. .srr files are created by a program called PyReScene which records exactly how a scene release is rar’d, and with what winrar version to re-create the original release format (rar’d) at a later date. Super useful program for reseeding and cross seeding stuff.