On Fri, May 1 at 11:44, Bob Friesenhahn wrote:
Hard drives are comprised of multiple platters, with typically an independently navigated head on each side.
This is a gap in your assumptions I believe. The headstack is a single physical entity, so all heads move in unison to the same position on all surfaces at the same time. Additionally, hard drives typically have a single channel, meaning only one head can be active at a time. With the nature of embedded position information on the same surface that contains user data, they haven't come up with a practical design for doing multiple concurrent reads from different places. At least one vendor (connor?) tried to do a 2-actuator disk drive, and it was a mechanical resonance nightmare for the servo systems. I think that what you're looking for, however, is already happening, with server farms moving to multiple 2.5" drives from the larger 3.5" drives. Even on SATA drives, with NCQ the rotational speed doesn't matter as much for overall throughput, so there are a growing number of server applications that will be utilizing traditional "laptop" form factor devices, to increase the spindle:capacity ratio without blowing out their space budget. SAS and SATA are both shipping greater and greater volumes of SFF devices. For the budget minded, a 2U server with a bunch of mirrored-pair 2.5" laptop drives is a nice platform, since you can fit 8-12 spindles in that box. The storage per unit volume is basically identical, just that you get 2-4x the spindle count. --eric -- Eric D. Mudama edmud...@mail.bounceswoosh.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
