Most of the drive can only be written sequentially. Attempts by the host to make a random write to a sequential area in an SMR drive will result in an error. Drive-managed mode hides this by letting you make random writes to the drive while the firmware translates that into sequential writes to the affected section. Host-managed mode means it's up to the operating system to do that.
In host-managed mode, if the OS wants to make a random write to the drive, it must query the drive to retrieve a pointer to the start of the sequential zone that contains the desired location, and then it must read that entire sequential zone, update it in memory with the new data, and re-write the whole thing.
Drive-managed mode is simpler: it just works. Host-managed mode is potentially higher performance: the OS can do more sophisticated read/write caching with a lot more memory to mitigate the performance penalties. Host-aware mode is kind of in between: the OS gets the new SCSI commands required to support host management if it wants to, but if the OS tries to write randomly to the drive, the firmware takes care of it instead of returning an error.
"Attempts by the host to make a random write to a sequential area in an SMR drive will result in an error."
What is "sequential area"? Just a block of several MB or GB in size? If a protocol and file system would allow 128MB clusters, it would greatly reduce overhead for the kind of tasks on any modern drive, even SSD.
Almost the entire drive falls into the sequential zone. The tracks overlap, and multiple tracks are grouped into a band. When you want to modify some random portion of a band, you need to basically (I'm simplifying) re-write the entire band.
Band size doesn't seem to be published by drive manufacturers, but I did find one whitepaper that studied a disk to figure it out. They found that a 5TB Seagate drive appeared to have a 36 MiB band size, but the whitepaper seemed to imply that the band size was variable depending on how close to the inner/outer diameter of the disk it was. Of course, host-managed drives would need to expose band size information to the host.
Using large blocks doesn't really solve the problem. For one thing, it wouldn't work with variable band sizes (and it'd have to be aligned). For another thing, you ultimately still have the same primary limitation, if you need to modify a 4 KiB chunk of data (or imagine log file updates where you frequently write less than 4 KiB to a file), you'd still need to rewrite 128 MiB of data to make your 4 KiB change.
Why are these drives still using 512-bit (emulated) sectors? It's 2017. 14TB drives should be allowing us to use 4k sectors. If you must use an OS that requires SMR support then you will also have support for 4k sectors...
Certainly, but I'm pretty sure the physical block size is more than 4 KiB. I'd LOVE to know exactly how big it is though (and is it even constant across the drive?). A CoW FS, like ZFS or Btrfs _ought_ to be able to work well with this.
The Helium is what really turns me off. Being a super light element it will leak over time.
Hoping that eventually we will have non-SMR, non-Helium, up-to 4 platters 8-10 terabyte drives at an affordable price, need to upgrade my limiting 5x 4TB external drives. I would prefer Western Digital drives... I was turned off by Deathstars years ago... Samsung spun off it's drive business... And Seagate would have to pay me to use their drives.
I'm quite sure WD/HGST/Seagate took the annoying habit from He to escape into account. So far I am impressed by the low energy consumption. And haven't heard of any He harddrive high outage rate. I have one so far and the next would definitely be He again.
They both approach it differently but I know Seagate uses wrought aluminum/forged casings to minimize permeability where as WD uses a cast aluminum vacuum molded with a bonding agent used to create a coating. Then there are multiple other coatings, high pressure bonding/seals, using lasers to weld them. Also the drives are at atmo to prevent the forcing of He in or out. They wont leak anything for at least 5yrs. Pressurizing them would force the He into microscopic cracks which would then enlarge and push out. A vacuum would have the opposite effect pulling gases in. Equilibrium prevents this and eases the burden on the seals. The key tech is the casings and the lack of defects in the mold/forgings.
Ultimately He is a stop gap for other tech. MAMR will help with densities but He is the only answer to the platter issues while maintaining the given 3.5 format for now.
I am sure a lot of that time was invested into how to utilize HE to increase profits. The presence of helium provides another, and very accurate means to control product durability.
So by engineering the product to control the amount of leakage they can fine-tune then the product will go bad, which naturally needs to be as soon as the warranty period expires.
Underbuilding other HDD components can often result in premature failures, which put a dent in the profits, as failures in the warranty period have to be replaced. In this regard, the controlled leakage of helium is a god-sent.
It is still too early to tell, but I have a feeling that HE drives will be very good at dying shortly after the warranty expires. Thus all those drives that remain perfectly operational for years after their warranty period runs out can be eliminated, thus promoting more sales and more profits.
You'd be surprised if you knew how much of the engineering goes not into making the product more durable, but into making it fail when it is most economically viable. All modern products come with multiple planned obsolescence fuses. For example, it was the sole motivation to promoting the "glass brick" phone design, as sealing the battery in a product extremely difficult to pry open and then put back together, guaranteeing that in 2 years of daily usage battery capacity will drop so low that most users would either make another purchase or pay for a ridiculously expensive "certified service replacement".
Helium drives have been around since 2013 (HGST He6). Based on the few public reports we have, it looks like it's at least as reliable as an air-filled drive. Hardly surprising given that the main reason to go for Helium, namely reduced turbulence has directly beneficial effects to reliability and durability. The rest of the drive (heads, motor, platter design and materials) is identical to classic air-filled drives, the literal only difference being how many platters are packed in the chassis (5 max in air (aside from Seagate's one-off 6 platter), 7-8 max in helium).
For your phone analogy, it's pretty crap tbh: all that a sealed battery does is make it a tad harder to open up for replacement, something a skilled (or even just patient) tech can handle fairly easily. Personally it's never been an issue for me though: I replace my phone due to insufficient specs well before the battery is worn out. I also haven't cracked any phone glass in 7 years of using phone with glass in em, 4 of those years being with phones with glass back too. That's with dozens of drops a year, onto everything from carpet to pavement, bitumen paved roads, gravel, concrete, marble, ceramic tiles and possibly worse.
Evidently, you lack the first grade math skills to put 2013 and 5 (years of warranty) together, to figure out whether or not helium drives come with a caveat will not be obvious before some time in 2018.
Which would explain why you are such an avid advocate of the benefits of planned obsolescence. You know, I can change my phone's battery in about 15 seconds, no especial skill or patience required, just like that. And even thou it is 4 years old now and I use it for more stuff you would possibly use a PC for ever, I don't feel the slightest bit constrained by the specs. Maybe because I use it to do actual work, and not just for bragging rights.
But good for you that you claim to haven't broken a glass brick phone in 7 years, although glass bricks weren't really a thing up until 3 years ago. Many people have broken them in their first week, on the first light drop, and guess what, warranty does not cover that, which explains the great amount of engineering that goes into making phones as brittle as possible.
Seems unlikely. There are surely factors like temperature, airflow, and altitude that affect how quickly helium leaks out. They would need to engineer the drives to last the warranty period in the worst case combination of those factors, resulting in many drives that would last much longer.
These drives come with operational ranges for altitude and temperature, and obviously, they'd test helium leakage in those ranges, adoy...
Also, they include a specific return rate figures in the price of each drive they sell, so corner cases are covered. The bulk of those drives operate in a fairly predictable environments, which is where the endurance fuse will be targeted at.
Presumably Helium is the easiest/cheapest gas to obtain, and possibly advantageous from a molecular dynamics PoV (sorry, I'm no physicist, so I can't really go beyond speculation here).
Less resistance and less turbulence from He than air, so you can pack in 7 or 8 platters, whereas air filled drives are limited to 5 platters. I assume that they chose helium over argon because helium is both lighter and cheaper than argon.
I stopped reading as soon as I saw the phrase "shingled magnetic recording technology". Yes, I know they said the drives are "purpose built for sequential writes". I don't care. It's too slow and SMRT is just another level of complexity that will ultimately reduce reliability.
this is the drive that i use for my backup server, one provider in europe offer me to use this one. its been 4 years, and until now my server https://62.210.11.53/ has zero problem. Bravo Western Digital
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32 Comments
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peevee - Wednesday, November 1, 2017 - link
"mainstream operating systems learn how to 'host-manage' SMR drives"What management is required?
Guspaz - Wednesday, November 1, 2017 - link
Most of the drive can only be written sequentially. Attempts by the host to make a random write to a sequential area in an SMR drive will result in an error. Drive-managed mode hides this by letting you make random writes to the drive while the firmware translates that into sequential writes to the affected section. Host-managed mode means it's up to the operating system to do that.In host-managed mode, if the OS wants to make a random write to the drive, it must query the drive to retrieve a pointer to the start of the sequential zone that contains the desired location, and then it must read that entire sequential zone, update it in memory with the new data, and re-write the whole thing.
Drive-managed mode is simpler: it just works. Host-managed mode is potentially higher performance: the OS can do more sophisticated read/write caching with a lot more memory to mitigate the performance penalties. Host-aware mode is kind of in between: the OS gets the new SCSI commands required to support host management if it wants to, but if the OS tries to write randomly to the drive, the firmware takes care of it instead of returning an error.
peevee - Wednesday, November 1, 2017 - link
"Attempts by the host to make a random write to a sequential area in an SMR drive will result in an error."What is "sequential area"? Just a block of several MB or GB in size? If a protocol and file system would allow 128MB clusters, it would greatly reduce overhead for the kind of tasks on any modern drive, even SSD.
Guspaz - Thursday, November 2, 2017 - link
Almost the entire drive falls into the sequential zone. The tracks overlap, and multiple tracks are grouped into a band. When you want to modify some random portion of a band, you need to basically (I'm simplifying) re-write the entire band.Band size doesn't seem to be published by drive manufacturers, but I did find one whitepaper that studied a disk to figure it out. They found that a 5TB Seagate drive appeared to have a 36 MiB band size, but the whitepaper seemed to imply that the band size was variable depending on how close to the inner/outer diameter of the disk it was. Of course, host-managed drives would need to expose band size information to the host.
Using large blocks doesn't really solve the problem. For one thing, it wouldn't work with variable band sizes (and it'd have to be aligned). For another thing, you ultimately still have the same primary limitation, if you need to modify a 4 KiB chunk of data (or imagine log file updates where you frequently write less than 4 KiB to a file), you'd still need to rewrite 128 MiB of data to make your 4 KiB change.
mooninite - Wednesday, November 1, 2017 - link
Why are these drives still using 512-bit (emulated) sectors? It's 2017. 14TB drives should be allowing us to use 4k sectors. If you must use an OS that requires SMR support then you will also have support for 4k sectors...takeshi7 - Wednesday, November 1, 2017 - link
Because some customers are stubborn as hell and refuse to drop 512 byte sectors.tommythorn - Wednesday, November 1, 2017 - link
Certainly, but I'm pretty sure the physical block size is more than 4 KiB. I'd LOVE to know exactly how big it is though (and is it even constant across the drive?). A CoW FS, like ZFS or Btrfs _ought_ to be able to work well with this.tommythorn - Wednesday, November 1, 2017 - link
Found it "256 MiB Zones". Wealth of info here https://www.hgst.com/sites/default/files/resources...The Linux kernel 4.13 already has (some?) support for these drives. Alas, without being able
to purchase them, it's an intellectual exercise.
peevee - Wednesday, November 1, 2017 - link
That would be a reasonable file size for media and big data storage (and everything else fits into 64GB SSD all taken together).mode_13h - Saturday, November 4, 2017 - link
That's nuts. I thought zones were supposed to be in the range of 10-40 MB.Wow. This is definitely for backups, then. Just forget about random-writes.
peevee - Wednesday, November 1, 2017 - link
"Why are these drives still using 512-bit (emulated) sectors?"Exactly. It is ridiculous. Almost all space is used by files well over 1MB in size.
ddriver - Wednesday, November 1, 2017 - link
FFS 15% capacity boost is not worth turning the product into garbage by incorporating SMR.takeshi7 - Wednesday, November 1, 2017 - link
Depends on the use case.mode_13h - Saturday, November 4, 2017 - link
I'm with you... sort of.You see, it still does random writes a fair bit better than tape. So, if that's the alternative, I'd have SMR in a heartbeat.
CaedenV - Wednesday, November 1, 2017 - link
So... basically you get awesome storage capacity, but major software issues and poor write performance due to SMR?Still, a single HDD that is larger than my whole RAID array... that is pretty awesome.
ddriver - Wednesday, November 1, 2017 - link
Or you can avoid all the cr@p and just get the 12 TB model adoy ;)Although I'd personally avoid the HE line and get an array of the 6 tb ultrastar 7k6000 for its reliability and durability.
StevoLincolnite - Thursday, November 2, 2017 - link
The Helium is what really turns me off.Being a super light element it will leak over time.
Hoping that eventually we will have non-SMR, non-Helium, up-to 4 platters 8-10 terabyte drives at an affordable price, need to upgrade my limiting 5x 4TB external drives.
I would prefer Western Digital drives... I was turned off by Deathstars years ago... Samsung spun off it's drive business... And Seagate would have to pay me to use their drives.
Foeketijn - Thursday, November 2, 2017 - link
I'm quite sure WD/HGST/Seagate took the annoying habit from He to escape into account. So far I am impressed by the low energy consumption. And haven't heard of any He harddrive high outage rate. I have one so far and the next would definitely be He again.Manch - Thursday, November 2, 2017 - link
They both approach it differently but I know Seagate uses wrought aluminum/forged casings to minimize permeability where as WD uses a cast aluminum vacuum molded with a bonding agent used to create a coating. Then there are multiple other coatings, high pressure bonding/seals, using lasers to weld them. Also the drives are at atmo to prevent the forcing of He in or out. They wont leak anything for at least 5yrs. Pressurizing them would force the He into microscopic cracks which would then enlarge and push out. A vacuum would have the opposite effect pulling gases in. Equilibrium prevents this and eases the burden on the seals. The key tech is the casings and the lack of defects in the mold/forgings.Ultimately He is a stop gap for other tech. MAMR will help with densities but He is the only answer to the platter issues while maintaining the given 3.5 format for now.
He research has been happening since the 60's
MrSpadge - Thursday, November 2, 2017 - link
That's why they've spent >10 years of R&D before they introduced He filled drives into the market.ddriver - Thursday, November 2, 2017 - link
I am sure a lot of that time was invested into how to utilize HE to increase profits. The presence of helium provides another, and very accurate means to control product durability.So by engineering the product to control the amount of leakage they can fine-tune then the product will go bad, which naturally needs to be as soon as the warranty period expires.
Underbuilding other HDD components can often result in premature failures, which put a dent in the profits, as failures in the warranty period have to be replaced. In this regard, the controlled leakage of helium is a god-sent.
It is still too early to tell, but I have a feeling that HE drives will be very good at dying shortly after the warranty expires. Thus all those drives that remain perfectly operational for years after their warranty period runs out can be eliminated, thus promoting more sales and more profits.
You'd be surprised if you knew how much of the engineering goes not into making the product more durable, but into making it fail when it is most economically viable. All modern products come with multiple planned obsolescence fuses. For example, it was the sole motivation to promoting the "glass brick" phone design, as sealing the battery in a product extremely difficult to pry open and then put back together, guaranteeing that in 2 years of daily usage battery capacity will drop so low that most users would either make another purchase or pay for a ridiculously expensive "certified service replacement".
ZeDestructor - Saturday, November 4, 2017 - link
Helium drives have been around since 2013 (HGST He6). Based on the few public reports we have, it looks like it's at least as reliable as an air-filled drive. Hardly surprising given that the main reason to go for Helium, namely reduced turbulence has directly beneficial effects to reliability and durability. The rest of the drive (heads, motor, platter design and materials) is identical to classic air-filled drives, the literal only difference being how many platters are packed in the chassis (5 max in air (aside from Seagate's one-off 6 platter), 7-8 max in helium).For your phone analogy, it's pretty crap tbh: all that a sealed battery does is make it a tad harder to open up for replacement, something a skilled (or even just patient) tech can handle fairly easily. Personally it's never been an issue for me though: I replace my phone due to insufficient specs well before the battery is worn out. I also haven't cracked any phone glass in 7 years of using phone with glass in em, 4 of those years being with phones with glass back too. That's with dozens of drops a year, onto everything from carpet to pavement, bitumen paved roads, gravel, concrete, marble, ceramic tiles and possibly worse.
ddriver - Sunday, November 5, 2017 - link
Evidently, you lack the first grade math skills to put 2013 and 5 (years of warranty) together, to figure out whether or not helium drives come with a caveat will not be obvious before some time in 2018.Which would explain why you are such an avid advocate of the benefits of planned obsolescence. You know, I can change my phone's battery in about 15 seconds, no especial skill or patience required, just like that. And even thou it is 4 years old now and I use it for more stuff you would possibly use a PC for ever, I don't feel the slightest bit constrained by the specs. Maybe because I use it to do actual work, and not just for bragging rights.
But good for you that you claim to haven't broken a glass brick phone in 7 years, although glass bricks weren't really a thing up until 3 years ago. Many people have broken them in their first week, on the first light drop, and guess what, warranty does not cover that, which explains the great amount of engineering that goes into making phones as brittle as possible.
mode_13h - Saturday, November 4, 2017 - link
Seems unlikely. There are surely factors like temperature, airflow, and altitude that affect how quickly helium leaks out. They would need to engineer the drives to last the warranty period in the worst case combination of those factors, resulting in many drives that would last much longer.Next time, try a bigger piece of tin foil.
ddriver - Sunday, November 5, 2017 - link
These drives come with operational ranges for altitude and temperature, and obviously, they'd test helium leakage in those ranges, adoy...Also, they include a specific return rate figures in the price of each drive they sell, so corner cases are covered. The bulk of those drives operate in a fairly predictable environments, which is where the endurance fuse will be targeted at.
Next time try doing a little more thinking first.
mode_13h - Monday, November 6, 2017 - link
Nah, brah. If there's an analysis that's lacking, I think it's yours.xchaotic - Saturday, November 4, 2017 - link
Can someone explain what does using Helium achieve? Why no other gas can be used, say Argon?ZeDestructor - Saturday, November 4, 2017 - link
Presumably Helium is the easiest/cheapest gas to obtain, and possibly advantageous from a molecular dynamics PoV (sorry, I'm no physicist, so I can't really go beyond speculation here).amosbatto - Saturday, November 4, 2017 - link
Less resistance and less turbulence from He than air, so you can pack in 7 or 8 platters, whereas air filled drives are limited to 5 platters. I assume that they chose helium over argon because helium is both lighter and cheaper than argon.keith3000 - Saturday, November 4, 2017 - link
I stopped reading as soon as I saw the phrase "shingled magnetic recording technology". Yes, I know they said the drives are "purpose built for sequential writes". I don't care. It's too slow and SMRT is just another level of complexity that will ultimately reduce reliability.MissMax - Sunday, May 9, 2021 - link
this is the drive that i use for my backup server, one provider in europe offer me to use this one. its been 4 years, and until now my server https://62.210.11.53/ has zero problem.Bravo Western Digital