Many examples of life writing could be considered primary sources. Primary sources are materials contemporaneous to the time you are researching, created by someone with first-hand experience of the phenomena that you are researching. Primary sources can come in any format, including newspaper articles, diaries, memoirs, letters, reports, scholarly articles, books (including works of fiction and non-fiction), films, artworks, laws, financial records, posters, photographs, and artifacts, and can be published or unpublished. Some originally unpublished primary sources (such as letters) are later gathered together by an editor for publication (for example Zora Neale Hurston : a life in letters).
Archives are materials created by people or organizations, in the course of their every-day activity, which are preserved because of their historical significance or value for research. Another definition of archives: unique constellations of materials, collected and preserved because they contain important information and/or evidence of their creator's responsibilities and actions.
Because primary sources (and life writing!) can come in any format, many databases and other places you would look for secondary sources are also good for finding primary sources. Examples of this include books in CLIO or HathiTrust. One way to find primary sources in these places is to limit by date to the period you're researching. Another is to use keywords (particularly in CLIO) such as memoir, autobiography, source*, documentary (which often refers to books of re-printed primary source materials), letters, etc.