Raid explained the best methodology I can find out there: http://www.thegeekstuff.com/2010/08/...evels-tutorial & http://www.pcmag.com/article2/0,2817,2370235,00.asp

In the numerous years I have had my system and all its memory moved from system to system, my tech has never lost anything for me. Yes I had a drive completely fail, but I had my system in a mirror setup and the other drive was fully operational and all assets were recovered. Yes to support Vaughan's statement we only crunching but some of us have other material on our systems which require retrieval if it ever fails.