--- Logical volume ---
LV Path                /dev/vg_space/vol_space
LV Name                vol_space
VG Name                vg_space
LV Status              available
# open                 1
LV Size                260.75 GiB
Current LE             66752
Segments               1
Allocation             inherit
Read ahead sectors     auto
- currently set to     256
Block device           253:0

--- Segments ---
Logical extent 0 to 66751:
  Type                linear
  Physical volume     /dev/sda5
  Physical extents    0 to 66751

original state:

   sda       sdb       sdc
 _______   _______   _______
|       | |       | |       |
|       | |       | |       |
|lv_orig| | empty | | empty |
|       | |       | |       |
|       | |       | |       |
|       | |       | |       |
|       | |       | |       |
|_______| |_______| |_______|


partition sdb & sdc, pvmove, then partition sda:

   sda       sdb       sdc
 _______   _______   _______
|       | |       | |       |
| sda1  | | sdb1  | | sdc1  |
| empty | | empty | | empty |
|_______| |_______| |_______|
|       | |       | |       |
| sda2  | |lv_orig| |lv_orig| <= linear on 2 drives
| empty | |half 1 | |half 2 |
|_______| |_______| |_______|


add sda{1,2,3} to vg, mirror the LV on this in striped mode:

   sda       sdb       sdc
 _______   _______   _______
|lv_orig| |lv_orig| |lv_orig|
|mirror | |mirror | |mirror |  <= striped!
|stripe1| |stripe2| |stripe3|
|_______| |_______| |_______|
|       | |       | |       |
| sda2  | |lv_orig| |lv_orig|
| empty | |half 1 | |half 2 |
|_______| |_______| |_______|



get rid of the sd{b,c}2 side of the mirror:

   sda       sdb       sdc
 _______   _______   _______
|       | |       | |       |
|lv_orig| |lv_orig| |lv_orig|  <= still striped!
|stripe1| |stripe2| |stripe3|
|_______| |_______| |_______|
|       | |       | |       |
| sda2  | | sdb2  | | sdc2  |
| empty | | empty | | empty |
|_______| |_______| |_______|


delete sd{a,b,c}2 partitions to extend sd{a,b,c}1 on the whole disk,
finally, extend the lv:

   sda       sdb       sdc
 _______   _______   _______
|       | |       | |       |
| sda1  | | sdb1  | | sdc1  |
|       | |       | |       |
|lv_orig| |lv_orig| |lv_orig|  <= definitely striped!
|       | |       | |       |
|bigger&| |bigger&| |bigger&|
|striped| |striped| |striped|
|_______| |_______| |_______|