Hi Tom, others,

>> Now the new multi-TB hard drives have 4096-byte physical sectors,
>> at least some of them try to act as if sector size were 512 bytes.
> virtually ALL disks act as having 512 byte sectors, even if they have
> internally 4096 byte ('advanced format').


> only recently 4kn drives became available
>  Seagate Enterprise Capacity 3.5 HDD 4Kn 6TB, SATA 6Gb/s (ST6000NM0004)
>  Toshiba MG04ACA500A

The newest 8 TB (!) HGST drives are produced in 4 variants now:
SAS or SATA, both available with 512 or 4096 bytes per sector.


A 10 TB variant is on the way, as far as I remember. But as said
by Tom, you are rarely forced to use 4k sectors unless you want.

>> So any modern OS needs to support at least 4096-byte sectors.
> it certainly doesn't hurt, but this is not urgent

For modern hard- and software, 4k sectors can be nice.

>> There really needs to be GPT support with hard drives that would have 
>> 4096-byte sectors.
> wrong. GPT is needed for drives with more then 4G sectors, which is
> disk size 2TB for 512 sector size, and 16 TB for 4K sectorsize.

Depends: I would assume that Windows 7 and up use GPT on fresh
installs even for disks of for example only 100 GB capacity. It
is more flexible to use GPT. So DOS should at least be aware of
GPT in the sense of not damaging existing GPT without some extra
warning in FDISK, for example. Being able to find FAT partitions
in GPT and actually use them would be very nice for DOS, maybe
even combined with the ability to boot from them.

>> Next step up from 4096 bytes could be 8k, 16k ...
> this will most likely never happen.

I agree. Using GPT completely side-steps the problem of having
too many sectors on a disk. Also, 4096 bytes happens to be the
page size of common processors and flash storage, so there is
not much reason to have "atomic storage units" larger than 4k.

Of course it is often faster to transfer multiple sectors in a
single I/O step, but I would not make those sectors bigger...

Regards, Eric

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