The Western Digital (formerly Hitachi) Ultrastar Datacenter series drives claim to have “triplestage actuator (TSA)”. At first I thought this was similar to the Seagate “dual actuator” drives as documented here. But then I found this pdf that explains:
The TSA makes use
of three pivot points: the Voice Coil Motor (VCM) Actuator, the Milliactuator and the Microactuator. Using three pivot
points enables a higher bandwidth servo control resulting in a more precise positioning of the head on the track.
With greater head position accuracy, tracks can be written closer together for higher TPI and greater areal density,
resulting in higher capacity HDDs.
So not the same thing and marketing-speak muddying the waters
I also found this blog entry claiming that the HC650 has dual actuators. But when I look on the product pages for HC650/HC670/HC680 I am unable to find any mention of “dual actuators”.
Does anyone know about these? Other than the Seagates are there any other HDDs with multiple actuators?
EDIT: oh I just discovered something, the blog entry I link to mentioned dual actuator for the “HS760” model, but when I clicked on that link it took me to the HC670 model. If I search on their site for “HS760” I find a link to “https://www.westerndigital.com/products/internal-drives/data-center-drives/ultrastar-dc-hs760-hdd?sku=ultrastar-dc-hs760-20-tb” but that is 404. If I search the internet for that model I find articles from Feb 2023 about it, but none for sale anywhere. Maybe it got cancelled?
Actuator stages are just joints within a head gimbal assembly of an arm group, All HDDs have been atleast dual stage for many decades. In the context of HDDs, “dual actuator” means two different arm groups that are independent and thus have twice the throughput of a single actuator hdd.
You are right that the HS760 is WD’s dual actuator drive, it is for sale to enterprise customers; I’ve never seen it for sale to normal consumers.
non enterprise customers given dual actuator drives are unworthy to understand its true glory!!! or something
this is super duper common. each head assembly has 3 stages of being able to sweep left to right to combat inertia, basically. That we have this level of control over a physical system is utterly insane.
Hard drives are a marvel of modern engineering; archeologists will no doubt find these things and not realize just how absolutely mind blowing these are and that they can make storing and retrieving trillions of discreet states look easy. They are a rube goldberg machine of data storage and no one has enough reverence and appreciation for what these commodity devices do on the daily. The authors that were inspired to write prose about the whirly brass machinery inside clocks and pocket watches should write an order of magnitude more eloquent prose about the wonders going in inside each and every mechanical hard drive today.
