[lvm-devel] [BUG-REPORT] mirror legs in the same PV with --alloc anywhere

[Alasdair G Kergon]

On Fri, Apr 16, 2010 at 02:22:09PM -0400, Takahiro Yasui wrote:
> I don't think the requirement '1s' is necessary, but  But I rather
> think that the policy 'normal' supports the following condition.
> 
>   1. The number of PVs must be more than the number of mirror legs,
>   2. M1 and M2 not on same PV as each other,
>   3. L1 and L2 not on same PV as each other,
>   4. L* may share PVs with M* if the number of PVs are less than
>      the total number of L* and M*.

I was thinking of changing it to default to the new policy, and renaming that to 'normal'.
(So the old normal is the one that gets a new name.)

I'm not sure that it would be easy to implement 4 within the existing normal policy.
In general, it's hard for a single policy to work towards (and choose between)
conflicting goals.  And 'number of PVs' is not easily defined.  (We're covering
cases like -m+3 as well, plus restrictions from available PVs supplied on the
command line, plus restrictions from which PVs are already in use at different
parts of the existing mirror legs.)

Alasdair