Status of support for 4KB disk sectors

Chuck Swiger cswiger at
Tue Jul 19 18:55:03 UTC 2011

On Jul 18, 2011, at 11:04 PM, Kevin Oberman wrote:
> I just wish FreeBSD had some decent documentation on such a fundamental
> operation. Fortunately there are some pretty good articles folks have
> written, but they did leave me with several questions.

Is there something in FreeBSD which is preventing you from using the drive's native DEV_BSIZE of 4096 bytes, or is it that the drive claims to have a physical block size of 512 bytes when it is really 4k?

Except for a PC BIOS maybe wanting a 512-byte boot sector, there shouldn't be anything magical about that sector size.  Unix operating systems like SunOS 3 and NEXTSTEP would happily run with a DEV_BSIZE of 1024 or larger-- they'd boot fine off of optical media using 2048-byte sectors, for example, and some of the early 1990's era SCSI hard drives supported low-level reformatting to a different sector size like 1024 or 2048 bytes.


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