Western Digital made quite a few bulletins yesterday associated to their enterprise hard-disk drives (HDD) product traces. While there was nothing sudden by way of the merchandise being introduced, two elements stood out – one was the retail availability of EAMR (energy-assisted magnetic recording) HDDs, and the opposite was extra info on the EAMR expertise itself. In 2019, WD had introduced the sampling of EAMR-based Ultrastar DC datacenter HDDs with 18TB and 20TB capacities. Yesterday’s bulletins construct upon these merchandise – the WD Gold-branded model of the Ultrastar DC CMR drives is now accessible for retail buy, and the Ultrastar drives themselves have moved to basic availability. The Ultrastar JBOD and storage server product traces have additionally been up to date to make the most of these new high-capacity drives.
Flash-based storage gadgets have taken over conventional shopper hard-drive utility areas. However, growing information storage necessities imply that HDDs nonetheless proceed to be essentially the most cost-effective resolution for bulk storage. HDD distributors have been engaged on growing laborious drive capacities utilizing a number of methods. Around 10 years again, we had 2TB 3.5″ HDDs with 5 PMR (perpendicular magnetic recording) platters in an air-filled enclosure. These drives had been CMR (typical magnetic recording) drives. In the final decade, we now have seen developments in three totally different classes which have enabled a 10-fold enhance within the capability of HDDs whereas retaining the identical bodily footprint:
Increasing the variety of platters / making the platters thinner has been made attainable by utilizing sealed helium-filled enclosures. The decreased turbulence permits platters to be stacked nearer to one another. The first-generation helium HDDs had 7 platters, and this has now grown to 9 platters for the brand new high-capacity drives.
The dimension of the writing head and the flexibleness with which it may be manipulated dictate the minimal width of the recording tracks on the platters. Western Digital is claiming that they’re the primary to make use of a triple-stage actuator (TSA) in delivery HDDs.
The enhanced precision with TSA permits the TPI issue to go up. Incidentally, Seagate additionally has a novel actuator scheme (twin actuator), although that’s aimed toward growing the throughput / IOPS.
One of the important thing challenges confronted within the quest to extend the areal density of platters is the power of the writing head to reliably alter the magnetic state of the grains within the tracks. Both heat-assisted magnetic recording (HAMR) and microwave-assisted magnetic recording (MAMR) are methods that handle this difficulty. In 2017, WD appeared set to go all-in on MAMR for his or her HDD product line, however three years down the highway, we’re taking a look at a variant that WD claims is a product of their HAMR and MAMR analysis – EAMR (energy-assisted magnetic recording).
While particulars had been scant when EAMR was introduced , WD is lastly opening up on among the technical elements.
WD’s first-generation EAMR expertise (christened as ePMR) entails the appliance {of electrical} present to the writing head’s important pole (that is along with the present despatched by the voice coil) throughout write operations. The extra magnetic subject created by this bias present ensures that the bits on the observe alter their state in a extra deterministic method. In flip, this enables the bits to be packed nearer collectively and growing the areal density.
The above methods can be used with shingled magnetic recording (SMR) to spice up areal density additional. SMR has been round in each host-managed and drive-managed variations for a number of years now. WD indicated…
