HDDs: PMR and TGMR - single manufacturer, economies of scale, centralised knowledge

[Zenaan Harkness]

> those of capacity ("any relevant level of
> capacity" perhaps?) cannot be duplicated in general.

> come civil war, very few will have the ability and capacity
> to create anything particularly useful, in a relevant time frame, to
> the defence of their family.


(Javascript site): https://zfsonlinux.topicbox.com/groups/zfs-discuss
[I cannot get this website to load the email archive at all, even with JS enabled - go figure; apologies for the lack of a functional link...]


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Re: [zfs-discuss] OFFICIAL WDC POSITION (Seagate too!): Re: Beware of SMR drives in PMR clothing:
Stoat<stoatwblr at gmail.com>  Sat, Apr 11, 2020 at 5:11 AM
Reply-To: Discuss <zfs-discuss at list.zfsonlinux.org>
To: Discuss <zfs-discuss at list.zfsonlinux.org>, Durval Menezes <durval.menezes at gmail.com>
Cc: stoatwblr at gmail.com

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Reminders:

-  LMR - Longitudinal magnetic recording (magnetic domain grains laying along the disk)
-  PMR - Perpendicular magnetic recording (magnetic domains stood up vertically - this was the last great density increase before SMR)
-  TGMR - Tunnelling giant magnetorestricive - this is a head technology needed to achieve PMR

  NB: ALL drives on the market at the moment are PMR with TGMR heads.  They all use the same platters and the same heads - there is only one manufacturer for each of those parts, despite there being three HDD makers

 -  SMR - Shingled magnetic recording. (More formally Shingled Perpendicular Magnetic recording)
 -  TDMR - "two dimensional magnetic recording" - this is a marketing term to say "zoned media" without coming out and saying it. You need zoning otherwise there aren't gaps between blocks of shingled tracks and you'd have to write a disk from one end to the other.


Coming soon (maybe)

-  patterned media (platters) - this will start separating the magnetic grains from each other to reduce crosstalk and improve density a little
-  HAMR/MAMR: heat assisted recording - needed because smaller grains need higher coercivity and the heads can't put out a magnetic field necessary to flip the field in the grains without heating them up to nearly their curie point in order to reduce that coercivity


The reason I say "maybe" is this: SSDs just killed HDD economics at all sizes


Micron have just dropped the price of their 5210 ION 8TB SATA archival SSDs to $700 apiece - and their 5200 Nearline/5300 daily SSDs aren't much more expensive. Then there's the NVME ranges...

They all have 5 year warranty, power loss protection and even the IONs are warrantied for _at least 0.2DWPD (4kB random writes) up to 0.9DWPD (large sequential fills) which fall nicely into 90% of both my home and enterprise requirements.
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This is an interesting bit:

> NB: ALL drives on the market at the moment are PMR with TGMR heads.  They all
> use the same platters and the same heads - there is only one manufacturer for
> each of those parts, despite there being three HDD makers

It appears that PMR and TGMR are sufficiently complex manufacturing, and the competition (and in this case, reducing economies of scale) becoming so low, that HDD manufacturers no longer have much competition between them.