The previous few years have seen loads of new improvements come up within the hard-disk drive market. For fairly a while, the HDD know-how roadmap was shared industry-wide – distributors launched new applied sciences at completely different time limits, however they have been all related in nature. As a current instance, HGST (now, Western Digital) was the primary to market with helium-filled HDDs, however each Seagate and Toshiba adopted up with related drives inside a couple of years.
Prior to 2017, there was consensus that heat-assisted magnetic recording (HAMR) would assist drive the rise in storage density for HDDs after conventional perpendicular magnetic recording (PMR) ran out of steam. Western Digital sprang a shock in This autumn 2017 by saying the choice to go together with microwave-assisted magnetic recording (MAMR) for future HDDs. Seagate, in the intervening time, has been all-in on HAMR and likewise launched 20TB HDDs based mostly on the know-how for enterprise clients (these HAMR drives are but to hit retail, although). In the in the meantime, Western Digital was promising MAMR drives for 16TB+ HDDs, however ultimately back-tracked in favor of energy-enhanced PMR (ePMR). Toshiba, however, launched flux control-MAMR (FC-MAMR) in its MG09-series of enterprise 16TB and 18TB HDDs.
At the HDD Reimagine occasion right now, Western Digital is introducing OptiNAND – a novel structure involving the mixing of an embedded iNAND UFS embedded flash drive (EFD) on the drive’s mainboard.
In conjunction, the corporate can be saying that it has been sampling its first 20TB non-SMR drives based mostly on OptiNAND-enabled ePMR to pick out clients, and that it might be adopting the OptiNAND platform shifting ahead for all 20TB+ HDDs. The firm additionally sees a path to 50TB OptiNAND-enabled ePMR drives within the second half of the last decade.
While the corporate didn’t quantify the quantity of NAND in its OptiNAND drives, they’re stressing the truth that it isn’t a hybrid drive (SSHD). Unlike SSHDs, the OptiNAND drives don’t retailer any consumer information in any respect throughout regular operation. Instead, the NAND is getting used to retailer metadata from HDD operation as a way to enhance capability, efficiency, and reliability.
Capacity
Western Digital’s OptiNAND announcement additionally conveys the truth that their 20TB 9-platter HDDs will proceed to make use of energy-enhanced PMR (ePMR). In addition to the usage of a triple-stage actuator to allow extra correct positioning of the heads over the tracks, the OptiNAND side is being touted as the important thing to enabling 2.2TB capability for every platter.
The enhance in areal density is being achieved by cramming the tracks on the platter nearer collectively (elevated TPI), whereas additionally shifting out a few of the metadata (each factory-generated and mid-user operation) out from the platter to the NAND. In explicit, Western Digital made a point out of the repeatable run out (RRO) recording of the pinnacle jitter / error place because the spindle revolves. This information (operating into a number of gigabytes) is generated within the manufacturing unit throughout manufacturing. It is often saved within the disk, taking over house that would have probably been used for consumer information. The OptiNAND structure strikes this to the NAND within the EFD.
One of the important thing challenges to packing tracks nearer collectively is the idea of ‘adjoining monitor interference’ (ATI). This ends in the necessity to periodically refresh information within the platter’s tracks because it might get corrupted by writes to adjoining tracks. Currently out there HDDs triggered these refreshes on a track-by-track foundation based mostly on the recording of write operations on the track-level. One of the downsides to rising areal density by rising the TPI is the necessity to do extra frequent refreshes. From refreshing as soon as in 10000 write operations in early HDDs, the slim tracks now must…
