Seagate has been testing a 16TB HAMR hot bit writing disk drive, with 20TB models in its sights.

HAMR stands for heat-assisted magnetic recording and it enables higher disk drive capacities by using smaller recording bits. The only practical way Seagate has found to keep the recorded bit's binary value (magnetic state) stable is by using a material which needs heating to make it writeable.

A laser diode heating element has been added to the drive's read:write heads and Seagate has been testing these and the recording medium to make sure it's a drop-in replacement for current PMR (Perpendicular Magnetic Recording) drives, with no loss of access speed, drive endurance or data value accuracy.

PMR drives will probably top out at 16TB capacity and be unable to support higher capacities, hence the need for a replacement technology.

Component trials have gone well enough for full-scale drive testing and the 16TB drive is part of that. Its capacity is 2TB higher than the current standard 14TB drives being produced. Western Digital has a 15TB drive but that uses overlapping write track technology (shingling) to get the extra terabyte, which means it's not a drop-in replacement for standard drives.

We expect 16TB standard – meaning non-shingled – PMR drives to arrive in 2019, with 20TB HAMR ones popping up in 2020, perhaps at higher capacities than that.

Jason Feist, Seagate's senior director of enterprise product line management, said: "Seagate has begun running early Exos HAMR units through the full set of standard benchmark tests used to prepare and optimize each new hard drive product for deployment.

"These are the same tests that customers use to qualify every new drive, including power efficiency tests, sg3_utils utilities that test SCSI commands to devices, standard smartmontools utility programs that will enable customers to characterize and compare HAMR drives in their environment right next to PMR drives, and several four-corners tests of reads, writes, random, sequential and mixed workloads."

Western Digital is using an alternative MAMR (Microwave-Assisted Magnetic Recording) to get to the smaller bit sizes needed for greater-than 16TB capacity levels. ®