Hamr HDDs are coming – Write heads with lasers increase capacity
The capacity of hard disks continues to increase steadily from year to year, but great leaps have not been made for a long time. In recent years, the growth in capacity has declined sharply. For example, the first 2TB HDDs became widely available in 2010 and from 2015 various manufacturers offered 8TB HDDs. Such a quadrupling of capacity has not occurred in the past five years. As a consumer, you can currently buy HDDs with a capacity of up to 18TB. In five years time, the maximum capacity has therefore grown by a factor of 2.25.
This declining growth is due to limitations of the perpendicular magnetic recording technique on which hard disks are based. The data density of such HDDs can hardly be increased, if at all. Manufacturers have therefore been working behind the scenes for years on alternative techniques, which should lead to major progress in the storage capacity of HDDs.
Seagate recently announced at the presentation of its quarterly figures that the first production HDDs based on the heat-assisted magnetic recording technique will be delivered at the end of this year. This technique uses lasers to write bits smaller on HDDs.
For the time being, there will be a limited amount of samples of 20TB HDDs, but from next year Seagate wants to increase its focus on such HDDs and the manufacturer expects the capacity of hamr HDDs to increase to 50TB in 2026.
Dates back to 2002. Seagate demonstrated a hamr-hdd in his lab at the time. In 2013 , the manufacturer was so optimistic that hamr HDDs were planned for 2014. However, the new technology is difficult to implement and that planning was not achieved. Competitor Western Digital has therefore opted for an interim solution under the name of energy-assisted perpendicular magnetic recording , which builds on the PMR technique. WD is also working on microwave-assisted magnetic recording, a variant of hamr , which is easier to apply.
Now that current HDDs are reaching their limits in terms of maximum capacity and new technologies are just around the corner, we take stock and look at the promises of the two largest HDD manufacturers.
Limitations of perpendicular magnetic recording
Traditional HDDs consist of platters made of an aluminum alloy. These are round discs with data tracks with magnetic fields on both sides to store bits. To increase the density, the magnetic fields stand upright on the disc surface, which gives the technique its name. The pmr technique is also called conventional magnetic recording , or cmr.
The maximum storage capacity of a hard disk is determined by the number of platters and the density of the magnetic fields. Manufacturers are now running up against the maximum achievable in both areas. The highest capacity 3.5″ HDDs currently use nine platters. To make that possible, hard drives must already be filled with helium. This has a lower density than air and produces less friction, making it possible to relatively placing many thin platters and writing on them with the moving writing heads.
PMR HDDs have been found to have a maximum density of approximately 1 terabit per square inch. If the magnetic fields for storing bits are made even smaller, stability will be compromised. The current nine-platter 18TB HDDs are approaching that limit.
Increase capacity with shingled magnetic recording
The capacity of HDDs can be stretched somewhat by applying shingled magnetic recording . This is a variant of pmr in which the data tracks on the platters are partly superimposed. That can increase the density by about 1.3x, but it also has disadvantages. It can negatively affect performance in applications with many random writes. Earlier this year, several HDD manufacturers were discredited because they appeared to be using SMR without mentioning it in the specifications.
Thinner platters of glass
Another way to increase the capacity of pmr hdds is to increase the number of platters. This could be done by using different material. In 2017 , Hoya already showed a prototype of a 3.5″ ten-platter HDD made of glass substrate with a thickness of 0.5 mm. To date, no ten-platter HDDs have been released, presumably due to the high cost.
Hoya announced in July this year that the company has sent samples of its thin platters to a manufacturer. This may indicate that an HDD manufacturer is working on a hard disk with ten platters. Whether and when it will be released is not yet clear. Glass platters have been used for some time in 2.5″ HDDs. However, those types of HDDs are becoming less and less popular. They are often used in laptops, which nowadays increasingly contain SSDs.
Major progress with energy assisted magnetic recording
With SMR and the addition of platters, there is still some flexibility in the current 3.5″ HDDs, but a really large growth in storage capacity is no longer possible. For even more storage capacity, the density of the data on the platters must be further This is possible with a number of techniques that have been in development for decades, the collective name of which is energy assisted magnetic recording , or EAMR, where the magnetic fields are manipulated before they are written, so that the bits can be made much smaller and the data density increases .
Hamr: heat assisted magnetic recording
As mentioned, Seagate has been working on HDDs based on heat-assisted magnetic recording for years . These hamr hdds are equipped with platters with a more stable magnetic material, consisting of an alloy of iron and platinum. Because this is more stable, the bits can be made smaller. However, the material is also much harder and to be able to describe that, it must first be heated to 400°C. Hamr HDDs use write heads with tiny lasers for that. Applying the hamr technique is complex, because the bits must be heated within a nanosecond and then cooled down again.
Hamr hdds have the same 3.5″ form factor as pmr hdds and are also interchangeable, but the use of laser requires new write heads and also requires the platters to be made of materials that can withstand heat. Manufacturers’ glass substrates Such as Hoya come in handy here again, according to the manufacturer, which can withstand temperatures of up to 700 ° C, while aluminum-based platters can withstand up to 200 ° C. The glass substrate is provided with a thin film with the magnetic material that can be written on.
According to SDK , also a manufacturer of glass substrate for platters, the density of hamr platters will reach 5 or 6 terabits per square inch in the future. This means that the data density is about five times higher than with PMR HDDs. SDK states that this will ultimately result in 3.5″ HDDs with a capacity of 70 or 80TB, without increasing the number of platters. Seagate also indicates that the data density of hamr HDDs will eventually be about five times as high as with pmr-hdds The manufacturer believes that the technology will last ten years.
Seagate: hamr is interesting from 24TB
Seagate will ship its first hamr HDDs at the end of this year. These are copies with a capacity of 20TB and they will not be produced in large numbers. With that capacity, the use of the new technology does not yet offer clear advantages over PMR or SMR HDDs, which are available with the same capacity. The hamr hdds are probably much more expensive due to the complex technology.
Seagate does not say which customers will receive the first hamr HDDs. These are probably large tech companies and data centers, so that they can experiment with them. According to Gianluca Romano, Seagate’s CFO, the transition to the hamr technique will be attractive if a capacity of 24TB is reached. Hamr HDDs with such a capacity should follow in the next calendar year, said the CFO when discussing the quarterly figures in October.
Seagate CEO Dave Mosley says the release of the 20TB variant is significant because it represents a technological milestone. According to the CEO, how many of the HDDs are delivered is not important. “The point is that the technology works and that we do exactly what we said: deliver a 20TB hamr hdd before the end of the calendar year.”
Mamr: microwave assisted magnetic recording
Another form of EAMR is microwave-assisted magnetic recording. This technique can use traditional aluminum platters with an alloy of cobalt and platinum on top, just like in PMR HDDs. By manipulating the magnetic layer with an electromagnetic field, it is possible to write the data with a higher density. Mamr HDDs work with microwaves generated by a spin torque oscillator located near the write head.
Western Digital said it was betting on mamr at the end of 2017, stating that the density of mamr HDDs could reach 4 terabits per square inch and that hdds with a capacity of 40TB would be released in 2025. At the time, the manufacturer expected to deliver the first mamr HDDs in 2019, but that has not happened so far.
In a promotional video at the time, WD emphasized the disadvantages of hamr HDDs; the need to heat the platters would make the technique unreliable and expensive. WD presented mamr as a reliable and cheap alternative.
In the meantime, WD seems to focus less firmly on mamr. At a technical presentation early this year , the manufacturer indicated that it sees both mamr and hamr as options for future hdds. However, the manufacturer will only use these techniques after 2023. In the coming years, WD expects to be able to release pmr and smr hdds with capacities of up to 30 TB.
Intermediate step: energy-enhanced perpendicular magnetic recording
Western Digital says it can further increase the capacity of its PMR and SMR HDDs by using EPMR. According to the manufacturer, this is a variant of traditional HDDs that partly uses techniques discovered during research into mamr and hamr hdds. WD intends to use these EPMR HDDs as a stepping stone to moving to full EAMR-enabled HDDs in the future.
WD has already implemented this in its Ultrastar DC HC550 18TB and in the HC 650 20TB variant. The former is a pmr hdd with a data density of 1022 gigabits per square inch and the second is a smr hdd with a density of 1160 gigabits per square inch. These hdds have a traditional write head, but when data is being written, it is put under current, which creates an extra magnetic field. This reduces the jitter and it is possible to write more accurately. Thus, the bits can be made smaller. WD wants to make two more generations of these energy-enhanced pmr and smr hdds and move to mamr or hamr after 2023.
Roadmaps and technical documents from Seagate and WD show the plans for the coming years. As mentioned, Seagate wants to release its first 20TB Hamr HDD this year and the company expects to use the Hamr technology from next year for more HDDs with higher capacities. Concrete plans for more hamr products have not yet been made public.
Western Digital still has pmr and smr hdds on its roadmaps until 2023, which are getting increasingly higher capacities. To achieve this, the manufacturer must already partly apply techniques that will later be used in mamr or hamr hdds.
Hamr or mamr hdd in your pc?
The concepts for hamr and mamr hdds are decades old, but the arrival of actual products based on the new techniques has been a long time coming. Said schedules of the hdd manufacturers have been missed more than once in the past.
It is unlikely that the new hdds will become available to consumers in the foreseeable future. Increasing storage density is especially important for data centers, where data hunger continues to grow. Although nothing is known about the prices of mamr and hamr hdds, it is likely that they are more expensive than pmr and smr variants, due to the complex technology.
With Seagate releasing its first hamr hdd, the go-ahead has been given. It is significant, however, that competitor WD will only venture into mamr or hamr in a few years’ time and will continue to build on existing techniques for the time being. So it remains to be seen whether the technology will develop quickly and gain market share.