Re: Block sizes for dd(1) to USB memory sticks (flash drives) for installers for FreeBSD

From: Warner Losh <imp_at_bsdimp.com>
Date: Wed, 05 Oct 2022 21:41:13 UTC 
On Wed, Oct 5, 2022 at 6:10 AM Pau Amma <pauamma@gundo.com> wrote:

> On 2022-10-03 08:26, Wojciech Puchar wrote:
> >> <https://www.freebsd.org/releases/13.1R/announce/#_availability> and
> >> elsewhere:
> >>
> >> bs=1m
> >>
> >> Why so small?
> > I've just checked. 128kB, 1MB and 4MB makes no noticable difference
>
> I remember someone in #freebsd (memory says debdrup) saying 128K is the
> largest amount FreeBSD will write to a file or device as a single unit.


maxphys used to be 128k. That changed in 13 to be 1MB (though it can be as
large
as 8MB).

However, the maximum transfer size often is 256k or 512k for USB thumb
drives
and in the cases where it's less than 1MB, we'll do less.

Warner