Converting linear to mirror using lvconvert seems to fail in some cases. Depending on the size of linear lv used and number of stripes, the extents seem to be miscalculated in some cases making the conversion fail when the total number of extents requested is not divisible by stripe count. 

The failing conversions shown below should work because the size is specified in units (M) and not exact extent count.


# pvcreate /dev/sd[bcdefgh]1
 Physical volume "/dev/sdb1" successfully created.
 Physical volume "/dev/sdc1" successfully created.
 Physical volume "/dev/sdd1" successfully created.
 Physical volume "/dev/sde1" successfully created.
 Physical volume "/dev/sdf1" successfully created.
 Physical volume "/dev/sdg1" successfully created.
 Physical volume "/dev/sdh1" successfully created.
# vgcreate vg /dev/sd[bcdefgh]1
 Volume group "vg" successfully created


Working conversions:

# lvcreate -L 400M -n lv1 vg
 Logical volume "lv1" created.

# lvconvert --type mirror --mirrors 1 --stripes 4 vg/lv1
 Using default stripesize 64.00 KiB.
 Logical volume vg/lv1 being converted.
 vg/lv1: Converted: 2.00%
 vg/lv1: Converted: 100.00%

=============================

# lvcreate -L 1g -n lv2 vg
 Logical volume "lv2" created.

# lvconvert --type mirror --mirrors 1 --stripes 4 vg/lv2
 Using default stripesize 64.00 KiB.
 Logical volume vg/lv2 being converted.
 vg/lv2: Converted: 0.39%
 vg/lv2: Converted: 100.00%

=============================

# lvcreate -L 750m -n lv3 vg
 Rounding up size to full physical extent 752.00 MiB
 Logical volume "lv3" created.

# lvconvert --type mirror --mirrors 1 --stripes 4 vg/lv3
 Using default stripesize 64.00 KiB.
 Logical volume vg/lv3 being converted.
 vg/lv3: Converted: 0.00%
 vg/lv3: Converted: 100.00%


Failing conversions:


# lvcreate -L 500M -n lv vg
 Logical volume "lv" created.

# lvconvert --type mirror --mirrors 1 --stripes 4 vg/lv
 Using default stripesize 64.00 KiB.
 Number of extents requested (125) needs to be divisible by 4.
 Unable to allocate extents for mirror(s).

=============================

# lvcreate -L 600m -n lv4 vg
 Logical volume "lv4" created.
# lvconvert --type mirror --mirrors 1 --stripes 4 vg/lv4
 Using default stripesize 64.00 KiB.
 Number of extents requested (150) needs to be divisible by 4.
 Unable to allocate extents for mirror(s).

=============================

# lvcreate -L 1100m -n lv5 vg
 Logical volume "lv5" created.
# lvconvert --type mirror --mirrors 1 --stripes 4 vg/lv5
 Using default stripesize 64.00 KiB.
 Number of extents requested (275) needs to be divisible by 4.
 Unable to allocate extents for mirror(s).



lvm2-2.03.05-2.el8.x86_64