Am 13.09.22 um 14:03 schrieb Pascal Hambourg:

On 13/09/2022 at 13:50, Reindl Harald wrote:

quoted

Am 13.09.22 um 13:48 schrieb Pascal Hambourg:

quoted

Legacy boot on GPT has some requirements, but it works

but we are talking about a LIVE-migration/reshape of existing disks 
with no place left for another partition

So what ? Aren't you going to create a GPT partition table on your 4-TB 
drives ? Else you won't be able to use the space beyond 2 TiB. (*)
A GPT partition table supports up to 128 partitions by default.

i won't have a choice as it looks like and so the easiest choice would 
be migrate /boot completly to a USB-stick and simply ignore the current 
/boot RAID1 which is just 482M small

since finally the new machines in the next step only support UEFI and 
the uefi-system partition can't live on a RAID it would end there over 
time anyways

the 4 machines are two pairs (homeoffice and office for two people) 
cloned by remove two drives and rebuild the array on both so the 
bbot-part is always identical and the stick on one can boot the other

so for now my last remaining question is "how would the command look for 
"Then with just two drives you change the raid to raid-1"

(*) In the DOS/MBR partition scheme, Linux supports that a partition 
ends beyond 2 TiB up to 4 TiB but this is a non standard trick and 
probably not supported by usual partitioning tools

meh