Linux Mint - constant disk activity?

Even when the machine is idle, there is activity to the disk.
What's the best way to figure out what's doing it?
Once I know that I can try to reduce or stop it.
I've attached htop output
Code:jonk@dave:~$ cat /proc/sys/vm/swappiness
10
jonk@dave:~$and
Code:jonk@dave:~$ free -h
total used free shared buff/cache available
Mem: 11Gi 1.8Gi 7.8Gi 191Mi 2.1Gi 9.4Gi
Swap: 2.0Gi 0B 2.0Gi
jonk@dave:~$and a bit more info about the disk
Code:jonk@dave:~$ sudo fdisk -l
[sudo] password for jonk:##########
Disk /dev/sda: 1.84 TiB, 2000398934016 bytes, 3907029168 sectors
Disk model: Hitachi HUA72302
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x289f73ed

Device Boot Start End Sectors Size Id Type
/dev/sda1 * 2048 1050623 1048576 512M b W95 FAT32
/dev/sda2 1052670 3907028991 3905976322 1.8T 5 Extended
/dev/sda5 1052672 3907028991 3905976320 1.8T 83 Linux

Disk /dev/sdb: 7.28 TiB, 8001563221504 bytes, 15628053167 sectors
Disk model: Backup+ Hub BK
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: D42CC68E-B160-4AE4-B6C6-828F95D96FBC

Device Start End Sectors Size Type
/dev/sdb1 2048 15628052479 15628050432 7.3T Linux filesystem
jonk@dave:~$and about the cpu
Code:jonk@dave:~$ lscpu
Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
Byte Order: Little Endian
Address sizes: 40 bits physical, 48 bits virtual
CPU(s): 16
On-line CPU(s) list: 0-15
Thread(s) per core: 2
Core(s) per socket: 4
Socket(s): 2
NUMA node(s): 2
Vendor ID: GenuineIntel
CPU family: 6
Model: 44
Model name: Intel(R) Xeon(R) CPU E5620 @ 2.40GHz
Stepping: 2
Frequency boost: enabled
CPU MHz: 1600.231
CPU max MHz: 2395.0000
CPU min MHz: 1596.0000
BogoMIPS: 4800.56
Virtualisation: VT-x
L1d cache: 256 KiB
L1i cache: 256 KiB
L2 cache: 2 MiB
L3 cache: 24 MiBand its running Mint 20 XFCE
Code:jonk@dave:~$ uname -a
Linux dave 5.4.0-40-generic #44-Ubuntu SMP Tue Jun 23 00:01:04 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
jonk@dave:~$
jonk@dave:~$ cat /etc/os-release
NAME="Linux Mint"
VERSION="20 (Ulyana)"
ID=linuxmint
ID_LIKE=ubuntu
PRETTY_NAME="Linux Mint 20"
VERSION_ID="20"
HOME_URL="https://www.linuxmint.com/"
SUPPORT_URL="https://forums.ubuntu.com/"
BUG_REPORT_URL="http://linuxmint-troubleshooting-guide.readthedocs.io/en/latest/"
PRIVACY_POLICY_URL="https://www.linuxmint.com/"
VERSION_CODENAME=ulyana
UBUNTU_CODENAME=focal
jonk@dave:~$
Attached Thumbnails