> On 9 Mar 2021, at 5:53 am, Dave C via macports-users
> <macports-users@lists.macports.org> wrote:
>
> Old technology drives use magnetism to hold bits. This works for decades, or
> so I’ve read. Usually the motor or bearings die before the magnetic medium
> fails.
>
> Solid State Drives use memory chips to hold bits. These “bit holders” can
> wear out after a few trillion transitions (changing from 1 to 0 and 0 to 1).
> I’d you’re using it in your laptop or PC, you’ll likely have no problems for
> many years. In an internet-connected server, you may exceed those maximum
> write cycles sooner rather than later.
>
Dave I was just reading up, interesting info …
SSDs work (as do eproms) by having an isolated ‘chamber’. You get electrons in
or out of the chamber using quantum tunneling [it disapears here and teleports
there] based on probability, higher with an electric field
Repeated used breaks down the insulation of the isolated ‘chamber’
SLC (the lowest capacity and most expensive) store 0 or 1 (volts or whatever
unit) and are most tolerant of damage
0 is 0, 1, 2, 3 units, 1 = 6, 7 8 units with 4 more likely a 0 and 5 more
likely a 1 (say)
DLC store 0, 1 2 ,3 units and are less tolerant of an extra, or a fewer u
TCL
DLC store 0, 1, 2, 3 … 13, 14, 15 units. Are the cheapest but most fragile ie
13 can leak away to 12, or gain from 13 to 14
But the link earlier is discuusion showed drives rated at 300 TBW going well
past that to 1 or 2 PBW (Peta is 1000 times Tera)
In use a HD (specially with lots of them) is more likely to fail than SSD.
Seagates old paper ‘ATA more than an interface’ says this:
Drive 1 seeks and the bump knocks others off track. They seek back knocking
others off track. Process continues until a disk fails.
Their 10 year old assesment of reasons is even more relevant on todays drives.
SSDs generally give more warning that ’the end is nigh’
All considered I’d take SSD for work disks and HD for long term backup
Heck in my day (ouch) we’d teach 'tower of hanoi' backup stratedgy using tape.
why not do likewise with HDs. Timemachine certainly make that easy.
James
> Dave
>
> - - -
>
>>> On Sun, 7 Mar 2021, Michael A. Leonetti via macports-users wrote:
>>>
>>> I’d really love to know more about what you’re saying here. Up until I just
>>> read what you wrote, I thought SSDs were the savior of HDDs.
>>
>> Real disk drives [tm] have their N/S magnetic poles lined up pretty much
>> forever; SSDs rely upon capacitors storing their charge forever (hah!).
>>
>> You need to have an electronics background to understand...
>>
>> -- Dave (VK2KFU)
>
