Status of support for 4KB disk sectors

Chuck Swiger cswiger at
Tue Jul 19 19:38:00 UTC 2011

On Jul 19, 2011, at 12:29 PM, Ivan Voras wrote:
>> 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?
> Nope, "only" that.


It's nice to have well-defined problems-- although it's perhaps not so nice when hardware is compelled to lie about its status because of backwards-compatibility (C/H/S vs LBA comes to mind also).

> The current state of the matter (i.e. for 9.0) is:
> * The new ATA driver has quirks for certain models of HDDs which have this false advertising (which can be manually triggered by which causes the drive to report stripesize of 4k.
> * This information is used in gpart to size & align partitions; it will be used by the new installer
> * Default fragment size for UFS was raised to 4K so it will be aligned by default.

Excellent; thanks for the detailed reply.


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