Understanding the rationale behind dropping of "block devices"

[Aijaz Baig]

Oh yes I was actually running an old release inside a VM and yes I had
changed the device names myself while jotting down notes (to give it a more
descriptive name like what the OSX does). So now I've checked it on a
recent release and yes there is indeed no block device.

root at bsd-client:/dev # gpart show
=>      34  83886013  da0  GPT  (40G)
        34      1024    1  freebsd-boot  (512K)
      1058  58719232    2  freebsd-ufs  (28G)
  58720290   3145728    3  freebsd-swap  (1.5G)
  61866018  22020029       - free -  (10G)

root at bsd-client:/dev # ls -lrt da*
crw-r-----  1 root  operator  0x4d Dec 19 17:49 da0p1
crw-r-----  1 root  operator  0x4b Dec 19 17:49 da0
crw-r-----  1 root  operator  0x4f Dec 19 23:19 da0p3
crw-r-----  1 root  operator  0x4e Dec 19 23:19 da0p2

So this shows that I have a single SATA or SAS drive and there are
apparently 3 partitions ( or is it four?? Why does it show unused space
when I had used the entire disk?)

Nevertheless my question still holds. What does 'removing support for block
device' mean in this context? Was what I mentioned earlier with regards to
my understanding correct? Viz. all disk devices now have a character (or
raw) interface and are no longer served via the "page cache" but rather the
"buffer cache". Does that mean all disk accesses are now direct by passing
the file system??

On Mon, Jan 16, 2017 at 12:41 PM, Greg 'groggy' Lehey <grog at freebsd.org>
wrote:

> On Monday, 16 January 2017 at  8:10:16 +0530, Aijaz Baig wrote:
> >
> > But when I check the disk nodes under /dev I get this
> > [CODE]ls -l /dev/*disk0
> > brw-r----- 1 root operator 14, 0 Jan 2 09:39 /dev/disk0
> > crw-r----- 1 root operator 14, 0 Jan 2 09:39 /dev/rdisk0[/CODE]
>
> Are you sure that this is FreeBSD?  The naming convention looks more
> like Mac OS, though the major device number doesn't match.  FreeBSD
> has been through a number of disk naming conventions, but I'm pretty
> sure that we never had anything as straightforward as 'disk'.
>
> > what was there earlier in FreeBSD before 'block device support' was
> > dropped?
>
> Apart from the name, things used to look similar.  Here a quote from
> "The Complete FreeBSD", written some time at the end of the last
> century:
>
> crw-r-----  1 root  operator    3, 131072 Oct 31 19:59 /dev/rwd0s1a
> brw-r-----  1 root  operator    0, 131072 Oct 31 19:59 /dev/wd0s1a
>
> The minor number included partition encoding, thus the large number.
>
> Greg
> --
> Sent from my desktop computer.
> Finger grog at FreeBSD.org for PGP public key.
> See complete headers for address and phone numbers.
> This message is digitally signed.  If your Microsoft mail program
> reports problems, please read http://lemis.com/broken-MUA
>



-- 

Best Regards,
Aijaz Baig