Rick Baer wrote:zCam does it directly on the cards. Its not that much voodoo as you think it is. cards are fast nowadays and if you can record to a samsung pro ssd its also super cheap.
It's not the speed of the cards that's necessarily the issue, it's the fact that all flash media can be written to a limited amount of times before it will fail. Writing to a card constantly when not recording will kill the card a lot faster.
For that reason I'm seriously doubting Z Cam writes the pre-roll to the card. It wastes power, it's less reliable, and is irresponsible use of the card.