[Bug 195174] New: bsdinstall(8) does not align partitions at 4k (or more)

bugzilla-noreply at freebsd.org bugzilla-noreply at freebsd.org
Wed Nov 19 19:08:05 UTC 2014


https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=195174

            Bug ID: 195174
           Summary: bsdinstall(8) does not align partitions at 4k (or
                    more)
           Product: Base System
           Version: 10.1-RELEASE
          Hardware: Any
                OS: Any
            Status: Needs Triage
          Severity: Affects Some People
          Priority: ---
         Component: bin
          Assignee: freebsd-bugs at FreeBSD.org
          Reporter: Mark.Martinec at ijs.si

Mark Martinec wrote (2014-10-10):
  https://lists.freebsd.org/pipermail/freebsd-stable/2014-October/080509.html

An install of a 10.1 from an installation ISO DVD. Apart from
choosing a ZFS filesystem, other options were left to their default.
In particular, the align-to-4k ZFS options was left enabled.

The ZFS really ended up with ashift 12, but neither the swap
nor the zfs partition is 4k aligned:

# gpart show /dev/ada0
=>       34  625142381  ada0  GPT  (298G)
          34       1024     1  freebsd-boot  (512K)
        1058    8388608     2  freebsd-swap  (4.0G)
     8389666  616752749     3  freebsd-zfs  (294G)

I find this unacceptable and surprising,
regardless of what the underlying media is.


Patrick M. Hausen wrote (2014-11-19):
  https://lists.freebsd.org/pipermail/freebsd-stable/2014-November/081080.html

I just installed a new machine with 10.1-RELEASE using the memstick
installer and chosing ZFS mirror root as the disk layout.

I did check the "4k" option, watched the installer do the necessary
gnop dance and the pool seems to be OK:
[...]
But this puzzles me a bit:
None of the start sector numbers is a multiple of 8, neither are
the end sectors a multiple of 8 minus 1.
So the pool uses a 4k block size but it starts on an odd multiple
of 2k on the platter - do I see this correctly?
[...]


In summary:

- the bsdinstall should align GPT partition as a bare minimum
  at a 4k boundaries regardless of the underlying media;

- in my opinion the first (freebsd-boot) partition should be
  aligned at 512kB with a size of 512kB, and all following
  GPS partitions should be aligned at 1 MB by default.

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