Emphasize that filesystem-level backups don't work#33102

DaveCTurner merged 2 commits intoelastic:masterelastic/elasticsearch:masterfrom

DaveCTurner:2018-08-23-snapshot-restore-is-how-to-do-backupsDaveCTurner/elasticsearch:2018-08-23-snapshot-restore-is-how-to-do-backupsCopy head branch name to clipboard