Status of support for 4KB disk sectors

Chuck Swiger cswiger at
Tue Jul 19 22:00:27 UTC 2011

On Jul 19, 2011, at 2:10 PM, Peter Jeremy wrote:
> On 2011-Jul-19 10:54:38 -0700, Chuck Swiger <cswiger at> wrote:
>> 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,
> Actually, Sun used customised CD-ROM drives that faked 512-byte
> sectors to work around their lack of support for anything else.

Hmm-- my brain could be fuzzy about things twenty-plus years ago.  But I remember booting a Sun3_35 or _60 from a non-Sun or Sun OEM'ed SCSI CD-ROM drive, probably a Plextor?

>> some of the early 1990's era SCSI hard drives supported low-level reformatting to a different sector size like 1024 or 2048 bytes.
> Did anyone actually do this?  I wanted to but was warned against
> it by the local OS rep (this was a Motorola SVR2).

Worked fine with 250MB Seagate ST1280 drives, and also a a 1GB Micropolis 2112.

It made a decent gain to available disk capacity (about 10-15%), and a smaller improvement to performance (about 5% IIRC).  It wouldn't work with drives using a dedicated embedded servo for sector positioning (ie, Quantum and DEC), but other vendors like Seagate used a normal platter surface for servo positioning, and you could reformat it with a different sector size.


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