Status of support for 4KB disk sectors

Kevin Oberman kob6558 at
Thu Jul 21 14:51:07 UTC 2011

On Thu, Jul 21, 2011 at 6:02 AM, Alexander Leidinger
<Alexander at> wrote:
> Quoting Kevin Oberman <kob6558 at> (from Tue, 19 Jul 2011 14:33:27
> -0700):
>> On Tue, Jul 19, 2011 at 1:41 PM, Alexander Leidinger
>> <Alexander at> wrote:
>>> On Mon, 18 Jul 2011 16:41:24 -0700 Jeremy Chadwick
>>> <freebsd at> wrote:
>>>> But the currently "known method" is to use gnop(8).  Here's an
>>>> example:
>>>> Now, that's for ZFS, but I'm under the impression the exact same is
>>>> needed for FFS/UFS.
>>> Info: gnop will not work for FFS/UFS because gnop is a temporary
>>> solution (needs to be done by hand at each reboot). For FFS/UFS you
>>> need to align the slice/partition and chose a good blocksize/fragsize
>>> combination (e.g. 32k/4k).
>> Thanks, Alexander.
>> This is what I had expected after reading the man pages, though I
>> would think -b 65560 -f 8192' would be a bit more reasonable in this
>> day of bloated file formats. it's been years since I have hit a
>> problem with lack of inodes.
> I suggest to test this somewhere first. I have no evidence that it can not
> work, but the blocksize/fragsize settings where subject to some unexpected
> results in the past when they where changed to a bad combination. IIRC this
> should be fixed now, but my memory may cheat on me...


Thanks for the advice. I would never try this on my system without a
clone of the disk, especially with the limited experience I have with
gpart and Lenovo's weird SYSTEM_DRV slice that seems to bite so many
people. (Still can't find any good explanation of what it's about, but
I do see a lot of incorrect ones.)
R. Kevin Oberman, Network Engineer - Retired
E-mail: kob6558 at

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