Convert LV to striped

To convert an lv from the usual linear to striped mode directly is not possible. It needs two steps: create a striped (old style) mirror lv and then remove the original pv from the mirror.

Given you have a vg vgdata with pv sdb and lv lvdata

First extend the vg with a new pv for each stripe, e.g. sdc and sdd for 2 stripes (pvcreate them first)

vgextend vgdata /dev/sdc /dev/sdd

If you want to reuse sdb as a stripe pv you'd have to move the data to one of the new pv's now

pvmove -n /dev/vgdata/lvdata /dev/sdb /dev/sdd

Next mirror the lv to the striped pv's

lvconvert --type mirror --corelog --mirrors 1 --stripes 2 /dev/vgdata/lvdata

Finally remove the linear part (sdb, or sdd if you pvmoved above) from the mirror lv

lvconvert --mirrors 0 /dev/vgdata/lvdata /dev/sdb

Check the result with

lvdisplay --maps --all /dev/vgdata/lvdata