From: Eric Auer <e.auer@jp...> - 2012-02-08 19:58:44
Hi Czerno / Bertho,
> Hi Eric! On the freedos-kernel list, you voiced such opinion about
> the future of big sector disks:
> " that has low priority imho, as drives with large sectors are a
> temporary thing, will be gone with GPT partitions. "
This refers to the following quote from an earlier 4 kB related mail:
> I stumbled upon a couple pages that say otherwise : "the industry"
> has agreed to sell AF disks only *until the end of 2014*!
It was actually you yourself who said that on 25 Jan 2012 ;-)
AF = Advanced Format = 4096 byte per sector, i.e. "Advanced"
meaning "if you find 512 byte better, you are not modern" :-p
It is a bit like APS Advanced Photo System - a nice buzzword
for a strange idea that is made look good for the end user.
Also, "advanced" format lets more data share less ECC error
correction data, squeezing out a tiny bit of extra capacity
and a bit of extra resistance to data errors...
Wikipedia claims that Windows Vista, 7 and 2008 have hotfixes
for "drives with natively larger sectors which allow access
in 512 byte emulated sectors" - in other words, the hotfix is
just fixing the performance loss caused by not knowing that
the underlying hardware sectors are big - while those Windows
versions apparently do NOT support native big sectors yet, at
least not for the boot drive... Reference for this:
In other words, Windows Vista / 7 / 2008 makes sure to always
access aligned blocks of 8 sectors of 512 bytes together, to
improve performance, when it knows that the physical disk has
4 kB sector size but uses 512 byte per sector I/O protocols.
That is very vaguely similar to what LBACACHE TICKLE and other
read-ahead tools can do for you, if configured properly... ;-)
> Manufacturers have no interest to reverting to 512 bytes sectors -
> since 4K sects allows them to advertise higher capacities
No. As Tom said, large sectors are only a workaround for WinXP
and similar "MBR partitioned" operating systems. With GPT, you
have no relevant limit to the number of sectors any more and
sectors can be small again :-)
On the other hand, everything is pretty virtual today anyway,
and SSD / flash have better performance with access in larger
blocks, but that does not mean that block has to equal sector.
It could also equal cluster and FORMAT already supports making
clusters of 4 kB or bigger align with 4 kB boundaries... ;-)
The "virtuality" will also mean that you eventually have to
load a "PC BIOS interrupts" legacy API module for EFI BIOSes.
Luckily those also exist as open source, if vendors get lazy.
PS: As you say you read this on freedos-kernel, but are only on
freedos-user (where you mailed) I took the freedom to CC both.