[linux-lvm] Mirror allocation policy

[Phillip Susi]

Alasdair G Kergon writes:

> On Tue, Jan 05, 2021 at 02:31:00PM -0500, Phillip Susi wrote:
>> How can I forge it to make the mirror on a single pv?  
>
> If --alloc anywhere isn't doing the trick, you'll need to dig into
> the -vvvv output to try to understand why.  There might be
> a config option setting getting in the way disabling the choice you want
> it to make, or if it's an algorithmic issue you might try to coax it to

I'm not seeing a whole lot here other than what appears to be this flat
out refusal to use extents from the same pv:

#metadata/lv_manip.c:2535         Not using free space on existing
 parallel PV /dev/md1.

Limiting the allocation to two specific extent ranges does not help either.

Full log:

#libdm-config.c:1061       Setting
 allocation/mirror_logs_require_separate_pvs to 0
 #metadata/lv_manip.c:3439         Adjusted allocation request to 7681
 logical extents. Existing size 0. New size 7681.
 #metadata/lv_manip.c:3442         Mirror log of 1 extents of size 8192
 sectors needed for region size 4096.
 #libdm-config.c:1061       Setting allocation/maximise_cling to 1
 #metadata/pv_map.c:54         Allowing allocation on /dev/md1 start PE
 2561 length 23039
 #metadata/pv_map.c:54         Allowing allocation on /dev/md1 start PE
 128000 length 347469
 #metadata/lv_manip.c:2321         Parallel PVs at LE 0 length 7680:
 /dev/md1
 #metadata/lv_manip.c:3186         Trying allocation using contiguous
 policy.
 #metadata/lv_manip.c:2788         Areas to be sorted and filled
 sequentially.
 #metadata/lv_manip.c:2704         Still need 7681 total extents from
 370508 remaining (0 positional slots):
 #metadata/lv_manip.c:2707           1 (1 data/0 parity) parallel areas
 of 7680 extents each
 #metadata/lv_manip.c:2711           1 metadata area of 1 extents each
 #metadata/lv_manip.c:2535         Not using free space on existing
 parallel PV /dev/md1.
 #metadata/lv_manip.c:3186         Trying allocation using cling policy.
 #metadata/lv_manip.c:2783         Cling_to_allocated is set
 #metadata/lv_manip.c:2786         1 preferred area(s) to be filled
 positionally.
 #metadata/lv_manip.c:2704         Still need 7681 total extents from
 370508 remaining (1 positional slots):
 #metadata/lv_manip.c:2707           1 (1 data/0 parity) parallel areas
 of 7680 extents each
 #metadata/lv_manip.c:2711           1 metadata area of 1 extents each
 #metadata/lv_manip.c:2535         Not using free space on existing
 parallel PV /dev/md1.
 #metadata/lv_manip.c:3186         Trying allocation using normal
 policy.
 #metadata/lv_manip.c:2783         Cling_to_allocated is set
 #metadata/lv_manip.c:2788         Areas to be sorted and filled
 sequentially.
 #metadata/lv_manip.c:2704         Still need 7681 total extents from
 370508 remaining (0 positional slots):
 #metadata/lv_manip.c:2707           1 (1 data/0 parity) parallel areas
 of 7680 extents each
 #metadata/lv_manip.c:2711           1 metadata area of 1 extents each
 #metadata/lv_manip.c:2535         Not using free space on existing
 parallel PV /dev/md1.
 #metadata/lv_manip.c:2783         Cling_to_allocated is not set
 #metadata/lv_manip.c:2788         Areas to be sorted and filled
 sequentially.
 #metadata/lv_manip.c:2704         Still need 7681 total extents from
 370508 remaining (0 positional slots):
 #metadata/lv_manip.c:2707           1 (1 data/0 parity) parallel areas
 of 7680 extents each
 #metadata/lv_manip.c:2711           1 metadata area of 1 extents each
 #metadata/lv_manip.c:2535         Not using free space on existing
 parallel PV /dev/md1.
 #metadata/lv_manip.c:3220   Insufficient suitable allocatable extents
 for logical volume : 7681 more required