Starting with 2025 non certified disks cannot be used on a Synology any more. If you try to create a storage pool the non certified disks will not show up and therefore cannot be selected for a storage pool. In the German magazin c't 2025/14 Mirko Dölle wrote an article which explains in detail how to create a storage pool with non certified disks and SSDs on a Synology on the command line. The following article just summarize the required commands without any detailed explanations to remind me how to get this done when I need these commands in the future. 

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Find new disks:

blkid | grep "/dev/[sn]"

Parition new disks according DSM requirements:

synopartition --part /dev/nvme0n1 1

synopartition --part /dev/nvme1n1 1

To check what's the paritions scheme of 15:

synopartition --list

Check which RAIDs exist:

mdadm -v --detail --scan

/dev/md0 has the root filesystem and and DSM firmware, /dev/md1 is swap space and /dev/md2 is available data space for volumes. /dev/md2 has a name with a following number, e.g. synology:2. For following command use next free number for name next free number for /dev/mdx. Given you have synology:2 and /dev/md2 use

mdadm --create /dev/md3 --level=1 --metadata 1.2 --name 'Enterprise:3' --raid-devices=2 /dev/nvme0n1p3 /dev/nvme1n1p3

to create RAID on the third parition on the new disks.

Now the new disks are displayed in the storage manager and can be used to create a storage pool.

In order to create multiple storage pools an LVM now has to be created.

Check which volume groups (VG) exist:

vgs

Now use next unused VG number in following command to create a VG on the prviously created RAID:

vgcreate vg2 /dev/md3

Next create logical volumet (LV) of 12m in the VG:

lvcreate -n "syno_vg_reserved_area" -L 12M vg2

Now restart the Synology and add additional volumes in the storage manager.

Note: These steps work as now on 6/29/2025 but may no longer work in the future due to DSM modifications by Synology.