4 ms·

Is there a reason you couldn't use a second set of actuators?

by kardos 10y ago

dom0 10y ago
There's kinda not enough space: https://upload.wikimedia.org/wikipedia/commons/thumb/7/75/Samsung_HD753LJ_03-Opened.jpg/1024px-Samsung_HD753LJ_03-Opened.jpg https://upload.wikimedia.org/wikipedia/commons/thumb/7/75/Sa... You could probably do it if the platter diameter were reduced, which would then accordingly reduce capacity as well. At that point you could just as well use two drives and also get lower overall failure probability. Or you use SSD caches, or memory caches, ...
- kardos 10y ago
  I was thinking of a Frankendrive with 5 actuators, which can do 5 parallel reads/writes, as long as they don't overlap. But the new dimensions would probably be the roadblock.
  - digler999 10y ago
    I was going to ask this too, but start with a simple 2nd voice coil on the opposite side of the spindle, keep the 3.5" form factor and just make it longer. My guess is the motion of one actuator would disrupt the airflow of the other, since we're talking about micrometer-ish (?) mechanical tolerances. This might be able to be mitigated by interleaving which side each arm wrote to. So the left arm's heads address the tops of the platters, the right side addresses the bottoms. Perhaps another option is to go back to the 1980's hdd designs where the arm moves straight down the radius of the platter. This design might permit multiple heads on the same arm. I'm sure all this stuff has been researched thoroughly. Either way, this doubles/triples the probability of mechanical failure
    - hga 10y ago
      Perhaps another option is to go back to the 1980's hdd designs where the arm moves straight down the radius of the platter. This design might permit multiple heads on the same arm. At my first job, sysadmin and programming on a PDP-11/44, 1-2 fascinating Winchester drives were procured for it. They had clear plastic covers, and you could see everything, the disk, the actuator, which had two heads, and it was by and large square, I'm almost positive it was rotary, not solenoid based straight stroke like many '70-80s drives, CDC's famous line in particular.
    - dom0 10y ago
      > since we're talking about micrometer-ish (?) mechanical tolerances. Even less than that. Tracks are 100-300 nanometers wide; the head flies about 3-6 nm above the platter. The actuator mechanism literally locks onto the signal encoded in the magnetic track and follows it as the platter rotates underneath the R/W head.
- kalleboo 10y ago
  No problem, just bring back the Bigfoot https://en.wikipedia.org/wiki/Quantum_Bigfoot https://en.wikipedia.org/wiki/Quantum_Bigfoot
- deleted 10y ago
  [deleted]

Is there a reason you couldn't use a second set of actuators?

by kardos 10y ago

Is there a reason you couldn't use a second set of actuators?

dom0 10y ago

There's kinda not enough space: https://upload.wikimedia.org/wikipedia/commons/thumb/7/75/Samsung_HD753LJ_03-Opened.jpg/1024px-Samsung_HD753LJ_03-Opened.jpg https://upload.wikimedia.org/wikipedia/commons/thumb/7/75/Sa... You could probably do it if the platter diameter were reduced, which would then accordingly reduce capacity as well. At that point you could just as well use two drives and also get lower overall failure probability. Or you use SSD caches, or memory caches, ...

kardos 10y ago
I was thinking of a Frankendrive with 5 actuators, which can do 5 parallel reads/writes, as long as they don't overlap. But the new dimensions would probably be the roadblock.
- digler999 10y ago
  I was going to ask this too, but start with a simple 2nd voice coil on the opposite side of the spindle, keep the 3.5" form factor and just make it longer. My guess is the motion of one actuator would disrupt the airflow of the other, since we're talking about micrometer-ish (?) mechanical tolerances. This might be able to be mitigated by interleaving which side each arm wrote to. So the left arm's heads address the tops of the platters, the right side addresses the bottoms. Perhaps another option is to go back to the 1980's hdd designs where the arm moves straight down the radius of the platter. This design might permit multiple heads on the same arm. I'm sure all this stuff has been researched thoroughly. Either way, this doubles/triples the probability of mechanical failure
  - hga 10y ago
    Perhaps another option is to go back to the 1980's hdd designs where the arm moves straight down the radius of the platter. This design might permit multiple heads on the same arm. At my first job, sysadmin and programming on a PDP-11/44, 1-2 fascinating Winchester drives were procured for it. They had clear plastic covers, and you could see everything, the disk, the actuator, which had two heads, and it was by and large square, I'm almost positive it was rotary, not solenoid based straight stroke like many '70-80s drives, CDC's famous line in particular.
  - dom0 10y ago
    > since we're talking about micrometer-ish (?) mechanical tolerances. Even less than that. Tracks are 100-300 nanometers wide; the head flies about 3-6 nm above the platter. The actuator mechanism literally locks onto the signal encoded in the magnetic track and follows it as the platter rotates underneath the R/W head.
kalleboo 10y ago
No problem, just bring back the Bigfoot https://en.wikipedia.org/wiki/Quantum_Bigfoot https://en.wikipedia.org/wiki/Quantum_Bigfoot
deleted 10y ago
[deleted]