Western Digital this week introduced its new Ultrastar DC HC620 family of hard drives that consists of 14 TB and 15 TB models. The HDDs use shingled magnetic recording (SMR) technology and are aimed at applications that need a lot of storage space, but are mainly read-focused operations. The manufacturer will only sell these products to customers with software that can manage SMR hard drives, primarily to those who already run 10 TB or 12 TB SMR HDDs.

The HGST Ultrastar DC HC620 hard drives are based on Western Digital’s fourth-generation HelioSeal helium-filled enterprise platform that packs eight platters and employing multiple enhancements of internal components specially designed to improve reliability and durability of HDDs working in vibrating multi-drive environments. The DC HC620 HDDs use eight SMR platters with a 1.75 TB and a 1.875 TB capacity featuring a 1034 and a 1108 Gbit areal density per square inch respectively. Because of a very high areal density, the 14 TB version of the drive offers up to 233 MB/s sequential read/write speed, whereas the 15 TB variant can hit 255 MB/s sequential read/write speed, which is the world record for any SMR HDD.

Keep in mind though how SMR technology works - it records new magnetic tracks partly overlapping the previously recorded tracks in a 'shingle roof tile' fashion. This method is appropriate for sequential writes, but as multiple tracks need to be adjusted when re-writes occur, it slows down the rewriting process. As a result, SMR-based HDDs are good enough for archive as well as write once read many (WORM) applications (think content delivery services), but is not suitable for typical server or enterprise workloads. Another thing to point out about high-capacity HDDs in general and Western Digital’s Ultrastar DC HC620 15 TB in particular is the fact that as capacities increase, IOPS per TB performance drops and it gets increasingly harder for operators of datacenters to guarantee their customers expected performance and quality of service. Therefore, while technically the Western Digital’s 15 TB is the world’s highest-capacity hard drive that exists today, it is necessary to understand that this is a very special product aimed at select customers with systems that take into account peculiarities of SMR and can mitigate lower IOPS per TB performance to minimize impact on QoS.

The Ultrastar DC HC620 HDDs feature a 7200 RPM spindle speed, a 512 MB DRAM buffer for indirection table management, a 7.7 ms read seek time, a 12 ms typical seek time, and a 4.16 ms typical latency. The manufacturer will offer the new series of HDDs with a SATA 6 Gbps or with SAS 12 Gbps interface. As for power, the DC HC620 SATA drives consume up to 6.4 W, whereas the DC HC620 SAS HDDs consume up to 8.3 W, which is in line with power consumption of their direct predecessor, the Ultrastar Hs14 (which in case of the 14 TB version of the DC HC620 is the same drive), but significantly lower than prior-generation of SMR HDDs from HGST.

Western Digital Ultrastar DC HC620 General Specifications
  HSH721415ALE6M0
HSH721415ALE6M4
HSH721415ALN6M0
HSH721415ALN6M4
HSH721414ALE6M0
HSH721414ALE6M4
HSH721414ALN6M0
HSH721414ALN6M4
HSH721415AL52M0
HSH721415AL52M4
HSH721415AL42M0
HSH721415AL42M4
HSH721414AL52M0
HSH721414AL52M4
HSH721414AL42M0
HSH721414AL42M4
Capacity 14 TB
15 TB
RPM 7200 RPM
Interface SATA 6 Gbps SAS 12 Gbps
DRAM Cache 512 MB
Format: Sector Sizes 4Kn: 4096
512e: 512
4Kn: 4096, 4112, 4160, 4224
512e: 512, 520, 528
Helium-Filling Yes
Areal Density 14 TB: 1034 Gbit/inch2
15 TB: 1108 Gbit/inch2
Sustained Transfer Rate 14 TB: 233 MB/s
15 TB: 255 MB/s
Average Latency 4.16 ms
Seek Time (read/write) 7.7/12 ms
Acoustics 2.0/3.6 Bels
Power Rating Idle 5.2 W 6.2 W
Operating 6.4 W 8.3 W
MTBF 2.5 million hours
Warranty 5 Years

Like other enterprise-class HDDs, the Ultrastar HC DC620 HDDs are rated for 2.5 million hours MTBF and come with a five-year warranty. Given the fact that the hard drives will only be sold to select customers, Western Digital does not publish per-unit pricing.

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Source: Western Digital

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  • Tchamber - Friday, October 26, 2018 - link

    "The manufacturer will only sell these products to customers with software that can manage SMR hard drives,"

    clearly, these aren't consumer HDDs, but what software does an SMR HDD require for management? Does Windows not recognize SMR?
    Reply
  • allenb - Friday, October 26, 2018 - link

    I used to work for a large company that’s very much in the target market for SMR. Our guys looked at it and made it work but ultimately you didn’t get enough from SMR vs either waiting slightly longer or accepting a bit less capacity with a conventional drive. Reply
  • vFunct - Saturday, October 27, 2018 - link

    Seems like SMR drives should really be 3x or more denser for all the custom work you need to do to make them work. Reply
  • xrror - Friday, October 26, 2018 - link

    I don't think the management requirement comes from the drive being SMR, it's because it's a "Host-Managed" drive.

    Which to me, "Host-Managed" = we couldn't figure out a way to have the integrated controller be performant across a wide range of usage scenarios, so we're pawning that off to the OS folks to treat this as glorified tape storage.

    I know that sounds mean, and I don't mean to downplay the engineers who made this drive possible. The fact that "Host-Managed" is even a thing honestly shows just how super hard it would be to make it "all rounder" performant - it might not even be possible.

    SMR really is the sacrifice of random I/O performance for capacity - which makes total sense, since these days if you need read/write perf you use solid state.
    Reply
  • RaduR - Saturday, October 27, 2018 - link

    These drives could be the drives that offer more backup for cloud servers. For sure there a ton of applications for these drives.
    The future for speed is for sure SSD (that are fast enough these days) but capacity will be magnetic. Why not mix those ?
    Reply
  • GreenReaper - Saturday, October 27, 2018 - link

    xrror gave the gist of this. It's possible to make an SMR drive that works well for certain use-cases and just-about-tolerably for others, but it won't be optimal for any of them - and in some cases (notably sustained random writes) the performance degrades catastrophically.

    There's been a fair amount of research on SMR over the past decade which analyzed the approaches and how they've been taken - not always successfully by the manufacturers.

    The OS or software, in theory, use its knowledge of the situation and the disk layout and capabilities to better-determine the ideal physical placement of the data and metadata being stored.

    To take a simple example: if you *know* you'll only ever write forwards - which might well be a use-case for "archiving" situations, e.g. Facebook content - you could theoretically provide maximum efficiency by simply having a single set of shingles, without any of the normal breaks that allow you to delete old data and reuse the space.

    You might alternatively create one shingle per variably-sized (but large) data blob - or use fixed sizes to decrease fragmentation, similar to a buddy memory allocator:
    https://en.wikipedia.org/wiki/Buddy_memory_allocat...

    This is the world of software-defined disk drives. It means hard drives become an increasingly specialized, bespoke form of storage - rather like tape.

    This kind of software/firmware mix happens in other areas, too, like CPU core boosting. Either the OS can do it or more recently it tends to tell tells the CPU to handle it and gives it hints about priority (processor core control). One or the other can be more optimal depending on the circumstances.
    Reply
  • linuxgeex - Sunday, October 28, 2018 - link

    My first experience with SMR was the Apple Disk][ Shugart drive. The write energy resulted in a track twice as wide as the head needed to accurately read it back. It was possible to step the drive by quarter tracks, and if you were careful with the track positioning - always step up past where you want to go then step down - then it was possible to write overlapping half tracks and read them back just fine. The problem came when you wanted to write to them again because every 1/2 overlapping track would get obliterated, because the read head was effectively over both at the same time. So you could squeeze 7 tracks into 4 tracks of space. If you dropped the gap between sectors and used the sector Prologue as the Epilogue as well, then it was possible to fit 22 sectors into a track instead of 16. Between the two you could fit slightly over double the total storage on a floppy. But there was a problem. You needed to hold all 7 tracks in memory at once, plus an MFM-encoded nybble buffer for one of the 7 tracks, which took basically twice the space once you also fit the prologues. So you needed 8x22x256 bytes = 45k of RAM to be able to write a single sector to the disk and that took about 63 revolutions at 360RPM, or about 200ms to read it and about the same to write it back. DOS required about 8k out of the system's 48k, about 4k was used by the OS and display hardware ($0000-$077) so it wasn't possible to do this without a 16k Language Card. So although this was great for archiving read-only stuff, it was way too inconvenient to catch on. But read-only you could have a floppy with double the data on it and surprise your friends by packing more games on a disk, and none of the mainstream disk copy programs could copy them... not even the bit-nybblers like Locksmith, because they didn't know how to rewrite the Epilogues. Reply
  • marras - Saturday, October 27, 2018 - link

    Windows does not recognize SMR disks as of now.
    That being said, if you know your having a SMR drive, you can easily mitigate the drive into eg. backup rutines. SMR is great for streamed writes, but the more random or deletes, the more they will be a bad choice. SMR is neither good for raid5+. The 512MB cache is to try to avoid too much of these random writes hits the disk.
    That being said, i had my fair experience with SMR disks and they work fine for my usage (backup).
    But, as others already wrote, then the SMR disks ain't worth it, vs the price they offer.
    SMR was promised in initial postings, that it would give 20% more space for same value.
    There already exists 14TB none SMR disks in the market, so we should see almost 17TB theoretical with SMR disks, OR we should see 14TB SMR disks with 20% less price.
    That's not what were seeing now..
    Reply

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