My understanding of SMR and CMR is that shrinking the write head further is increasingly difficult/impossible, so SMR can enable 2~3x the data density by allowing the larger write head to overwrite multiple tracks.
However, I only ever see SMR in low-density drives, and HAMR isn’t supposed to have been ready for market by the time these much higher capacity CMR drives were a thing.
What technology advantage do they have over SMR drives that enables such high data density, and why can’t that same technology be deployed with SMR to enable even higher density?
The higher density CMR drives pretty much universally have a Helium filling and sealing instead of the standard “normal air” inside the drive. The Helium makes it possible to use more platters (i.e. the spinning element that actually holds the data) per drive, which would not be possible on regular air. Helium has less density and so less air resistance for the platters, which is why more platters can be used.
I understand Helium but why isn’t helium used to improve density of SMR drives if it makes such a huge impact that a CMR drive could outstrip a SMR drive in the same space by more than 2:1?
Basically, why don’t we have 60GB helium SMR drives? I’ve heard of SMR being used with Helium as far back as 2014 already, but why not today?
I could understand HAMR, because it’s basically a replacement for the magnetic write head as far as I understand it? But, it seems like there’s something missing here that I’m just not getting.
Not sure about that. My guess would be that the R/W-Head for SMR is different enough and/or bigger that it can’t benefit from the more platters that Helium allows anyway.
Helium is a noble gas and it’s expensive to obtain and pack into a drive. And even if it reduces the rotational friction compared to air you’re still “fighting” the limitation of the motor that spins the platters and the speed of the heads.