Seagate delivers 20 TB hard drives from the Exos X20 and IronWolf Pro series. The highlight: For the first time, there are ten instead of nine magnetic disks (platters) in the 3.5-inch housing. Seagate has a capacity of 20 Tbytes without having to use complex tricks to increase the data density on a magnetic disk.
Both models use conventional magnetic recording (CMR) without overlapping data tracks. Only a helium filling is used to reduce undesirable flow effects in the HDD housing. With price recommendations from 665 euros, Seagate’s 20 TB hard drives are primarily intended for servers and (cloud) data centers.
In the case of ePMR, an electric current is passed into the write head in order to generate an additional magnetic field and thus reduce the so-called jitter, which in turn enables a more detailed description of the platter. OptiNAND hard drives contain several dozen GB of flash memory. Metadata and user data are on this NAND flash instead of on the magnetic disk, which means that they can be controlled more precisely and also described more closely.
Increasing data density
The WD Gold 20 Tbytes and WD Ultastar DC HC560 20 Tbytes use nine platters with 2.2 Tbytes of storage space each. With a tenth magnetic disk, around 22 Tbytes are expected in 2022. For 30 TB, the capacity of a magnetic disk has to increase by around 36 percent – Shingled Magnetic Recording (SMR) with overlapping data tracks may then play a role.
As Anandtech noticed, Meanwhile, Western Digital does not say a word more about the microwave technology Microwave Assisted Magnetic Recording (MAMR), which should have been used in series models since 2020, but was then replaced by ePMR as an intermediate step. Like Seagate, WD will focus in future on Heat-Assisted Magnetic Recording (HAMR), a further development of the ePMR principle.