A new report indicates that HAMR disk drives may offer lesser increased potentials at larger capacities when SMR is applied. Seagate recently announced its Exos 30 TB+ hard drives which are based on the Mozaic 3+ HAMR platform. This new technology is bringing storage capacities never seen before in a single drive but, according to this report, it may already be susceptible to its own version of Moore’s Law. The new report from Blocks and Files indicates that increased storage capacity potentials at, or above 30 TB may be related to the width of read and write tracks.
Per Blocks and Files:
“The larger the difference between write track width and read track width, the bigger the capacity advantage delivered by shingling. The implication is that there is less scope for shingled capacity addition on HAMR or higher capacity drives because the write tracks are not that much wider than the read tracks.”
Block and Files report notes how using HAMR technology allows 24 TB PMR drives to get a capacity increase of 16.66% to 28 TB. However when SMR is brought into the mix a 30 TB HAMR drive only sees an increase of 2 TB, or 6.66%. Seagate was asked about this peculiarly seeming ratio disparity and Director of Product Line Management Jason Zimmerman Sr. said “The Mozaic 3+ product offerings are not necessarily completely indicative of the overall SMR vs CMR,” and that “Generally, with Mozaic 3+, we are observing approximately ~10 percent additional capacity gains with SMR over CMR.”
Jason acknowledges the 6% difference but adds it should not be considered “indicative of the technology capability”. This could be alluding that there will be varying ratios at different capacities and it was previously mentioned in another announcement regarding HAMR drives that they could reach as much as 50 TB of storage. Jason also says that while Block and Files’ “observation” is correct regarding the size of the tracks (TPI) with CMR having diminishing returns with SMR but that relationship is not dependent on the type of recording technology used, be it either HAMR or PMR.