Dear Dave,

thank you for your response.

Here is my output:
$ sudo lvs -o segtype cryptdata_raid5/home
   Type
   linear
   linear
   linear

And if I execute:
"$ sudo lvconvert --type raid5 -i 3 cryptdata_raid5/home"
I get
   Using default stripesize 64,00 KiB.
   Replaced LV type raid5 (same as raid5_ls) with possible type raid1.
   Repeat this command to convert to raid5 after an interim conversion 
has finished.
   Are you sure you want to convert linear LV cryptdata_raid5/home to 
raid1 type? [y/n]: y
   Insufficient free space: 1 extents needed, but only 0 available

So probably I hit a bug with lvm2-2.03.12 on arch linux.

Thanks for your help.
Then it will be better to reformat my RAID5 with mdadm.

Am 29.07.21 um 16:59 schrieb David Teigland:
> On Wed, Jul 28, 2021 at 11:50:56PM +0200, Martin Dünkelmann wrote:
>> Dear LVM2-People,
>>
>> I made a native RAID5 via LVM on 3 SSDs without mdadm, since LVM2 can do it
>> natively.
>>
>> But I got confused about how to easily monitor it (send emails about errors,
>> since it's a remove server) and how to check, repair and scrub the RAID5.
>>
>> Using:
>> "sudo lvchange --syncaction check cryptdata_raid5/home" (same for repair)
>> results in
>>
>> Command on LV cryptdata_raid5/home does not accept LV type linear.
>> Command not permitted on LV cryptdata_raid5/home.
> It works for me, so it could be a fixed bug.  Check that the LV is really
> raid5: lvs -o segtype cryptdata_raid5/home
>
>> Does that mean LVM2 doesn't fully support native RAID5 and I should format
>> everything and set up a mdadm raid5?
>> Because mdadm has scrubbing and email reports according to the mdadm.conf.
> Right, mdadm does much more.
>
> Dave
>
-- 
Greetings

Martin