d-i now creates aligned partitons (at least for msdos disk labels),
using a 1MiB granularity.

Unfortunately, d-i is letting LVM2 use its default metadata size for the
PVs, which is 192KiB.  This causes the first usable PE to be
out-of-aligment on anything but 64KiB and smaller stripes (and erase
blocks).  The end result is that LVs are created out-of-alignment, and
thus anything that uses that LV will also be out-of-alignment.

Please force pvcreate to alocate enough metadata to align the first PE
to a 1MiB boundary, to match what the d-i partitioner is doing.

Note: it would be better if we could tell d-i what target to align for
(for partitions, LVM PVs *and* filesystems), which would allow one to
waste less space to alignment.