from the never-enough-storage dept.
The Register asked Seagate's Director of Technology Strategy and Product Planning Jason Feist about the company's plans to use multi-actuator technology in upcoming hard disk drives. Seagate insists that the technology can double input/output operations per second (rather than increasing it by, for example, 1.8x), and says that customers have validated the concept:
Howard Marks, founder and chief scientist at Deep Storage Net said: "We've had drives with 2 positioners before (IBM 3380 - one set of heads were dedicated to inner tracks, the other to outer tracks). That was back in the day of linear voice coils so they came from opposite sides of the 14-inch platters."
He identifies a software issue with Seagate's multi-actuator single pivot design: "Most storage software including logical volume managers and file systems, are built with the knowledge that a disk drive can only have it's heads in one place at a time and their queuing logic may mismatch with the multipositioner logic." This means: "It may not double throughput for large I/Os."
It could get close though, as "I understand that Seagate is going to make these look like 2 logical drives via a driver. That should solve #1 above and let systems get 1.8-1.9X IOPS."
[...] El Reg: What are your ideas and thoughts about multi-actuator disk drives and the arguments for and against them?
Jason Feist: We are bullish on this technology. A number of key customers have validated the concept and are working closely with us on the development of the technology.
Hyperscale data center service-level agreements (SLAs) are a critical factor in defining storage deployment needs and designing next-generation technologies that efficiently support storage deployments. In order for TCO (total cost of ownership) to continue to improve, the IOPS of a disk drive need to increase along with the capacity increases we're enabling with new areal density advancements.
The small cost adder that is required for additional components to deliver this performance gain is a much more cost-effective solution than using additional drives/spindles. The hard drive and SSD have a strong relationship in a data center, and both are required to achieve capacity and performance requirements at scale.
The IOPS growth provided by Multi Actuator technology in disk drives enables this relationship to continue to scale into the future.
Future Seagate HDDs will begin including two separate sets of actuator arms that can operate independently in order to double read/write speeds:
Seagate's multi-actuator technology is a simple concept, and the idea certainly isn't new. In fact, the company has already developed drives with multiple actuators in the past, but they weren't economically viable due to higher component costs.
Most HDDs read and write data to and from multiple platters. For instance, Seagate's largest drives wield up to 8 platters and 16 heads. The heads, which are connected to the end of an actuator arm assembly, read and write data from both sides of each platter.
Unfortunately, those 16 heads are all aligned on the same arm, which means they all move in unison. Simultaneously aligning all the heads on all the platters isn't possible because of the incredibly thin data tracks on the platters, so only one of the heads is actively reading or writing data at any given time. That limits read/write throughput and performance with randomly accessed data.
Seagate's new design uses two sets of actuator arms that operate independently. Each carries eight heads. That means the drive can read or write from two heads at once, provided they are attached to different actuator arms. The drive can respond to two commands in parallel and one head can read while another writes, or both can read or write simultaneously.