Device                                                                  Boot      Start        End    Sectors  Size Id Type
/dev/disk/by-id/nvme-Samsung_SSD_970_EVO_Plus_1TB_SERIALNO-part1            2048 1279264767 1279262720  610G 83 Linux
/dev/disk/by-id/nvme-Samsung_SSD_970_EVO_Plus_1TB_SERIALNO-part2      1279264768 1547700223  268435456  128G 82 Linux swap / Solaris
/dev/disk/by-id/nvme-Samsung_SSD_970_EVO_Plus_1TB_SERIALNO-part3      1547700224 1816135679  268435456  128G bf Solaris   CACHE / L2ARC
/dev/disk/by-id/nvme-Samsung_SSD_970_EVO_Plus_1TB_SERIALNO-part4      1816135680 1953525167  137389488 65.5G bf Solaris   LOG / ZIL

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https://www.mail-archive.com/zfs-discuss@opensolaris.org/msg34674.html

Approximately 200 bytes per record. I use the following example:
        Suppose we use a Seagate LP 2 TByte disk for the L2ARC
                + Disk has 3,907,029,168 512 byte sectors, guaranteed
                + Workload uses 8 kByte fixed record size
        RAM needed for arc_buf_hdr entries
        + Need = ~(3,907,029,168 - 9,232) * 200 / 16 = ~48 GBytes
-->

( 268435456 - 9,232) * 200 / 16 = ~3.4 GBytes

zpool add risa cache /dev/disk/by-id/nvme-Samsung_SSD_970_EVO_Plus_1TB_SERIALNO-part3
zpool add risa log /dev/disk/by-id/nvme-Samsung_SSD_970_EVO_Plus_1TB_SERIALNO-part4

        logs
          nvme-Samsung_SSD_970_EVO_Plus_1TB_SERIALNO-part4  ONLINE       0     0     0
        cache
          nvme-eui.002538510140b872-part3                          ONLINE       0     0     0