Re: hdparm -B meaning
Either of those is best used for an alternate drive that you are not actively using. -S allows you to set an actual time until spin down. My desktop apparently does not support -B, but -B 1 is the most frequent power management when that is supported.
If you are using programs that access data (along with delayed writes), or have a firewall that constantly logs or something else logs regularly, it would be somewhat pointless because your drive will have to regularly spin right back up. Without anything else reading, writing, or logging, cron just logs hourly.
i5 650 3.2 GHz, 8 GB, nvidia GTX 750 Ti, 32" 1080p | i7-4700MQ, 8 GB, Intel HD 4600/nvidia GTX 765M, 15.6" 1080p | etc.