GPT partitions not 4k aligned by 10.1-RC1 installer

Mark Martinec Mark.Martinec+freebsd at
Fri Oct 10 02:06:54 UTC 2014

Today I did a quick install of a 10.1-RC1 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.

Guess what, 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.

Now that even Windows is aligning partitions to 1 MiB,
and SSD erase block is often cited as 1 MiB ...

Worried about space waste of half of one JPG photo?


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