The pvcreate(8) manpage does not list a default for --dataalignment,
could you add it? There is also no default listed for
--dataalignmentoffset (I assume it's zero?) maybe that would be good to
add too.

The vgcreate(8) man page does list a default of 4 MB for
--physicalextentsize but does it really use that as the default always
or is it smart enough to look at what the pv is using for
dataalignment? It might help to add some clarifying text there too.

The reason (for me) that it would be good to have this info is
when trying to ensure that the various levels of the stack (partition,
md,luks,pv,vg,lv) are aligned for optimal performance.

Thanks,

Matt Taggart wrote on 24 Mar 2011:
*t

Tomas Pospisek writes:

OK, so
1) pvcreate(8) still needs to list defaults for --dataalignment and
--dataalignmentoffset

2) without going into too much specifics about tuning, I think the
vgcreate(8) man page should probably mention something like

  "physicalextentsize should be equal to or larger than, and a multiple of
the PV dataalignment setting"

but someone who understands the tuning issues can probably improve on the
above.

Thanks,

Hello Matt,

I *think* if you want to improve lvm's docu the most effective action
would be to take these suggestions upstream [1]: while I am not
sufficiently informed on the state of lvm maintenance in Debian, I see
that there hasn't been any action on various bug reports/patches in its
bug tracker that naively would seem to be easy to act on. Meanwhile from
the few bug reports upstream that I have looked at, I got the impression
that upstream is quite responsive.

@Debian LVM maintainers:

I very much appreciate your effort and am thankful that I am able to use
lvm in Debian. In my above comment I do not want to imply any judgement on
the quality of the maintenance of lvm.

Thanks,
*t

[1] https://www.sourceware.org/lvm2/