Debian-4.9.0-mvebu: constant writing to disk (no replies)

Hello,

I am using my NAS326 with a USB flash stick to boot from with Kernel linux-4.12.4-mvebu-tld-1 and Debian-4.9.0-mvebu-tld-12-rootfs-bodhi.tar.bz2

As always when using flash memory I look if something is writing frequently to this disk.

And I found this:

root@nas326:/boot# iotop -obtqqq
15:40:03     7 be/4 root        0.00 B/s    0.00 B/s  0.00 % 99.99 % [ksoftirqd/0]
15:40:05     7 be/4 root        0.00 B/s    0.00 B/s  0.00 % 99.99 % [ksoftirqd/0]
15:40:07     7 be/4 root        0.00 B/s    0.00 B/s  0.00 % 99.99 % [ksoftirqd/0]
15:40:09     7 be/4 root        0.00 B/s    0.00 B/s  0.00 % 99.99 % [ksoftirqd/0]
15:40:11     7 be/4 root        0.00 B/s    0.00 B/s  0.00 % 99.99 % [ksoftirqd/0]
15:40:13     7 be/4 root        0.00 B/s    0.00 B/s  0.00 % 99.99 % [ksoftirqd/0]
15:40:14     7 be/4 root        0.00 B/s    0.00 B/s  0.00 % 99.99 % [ksoftirqd/0]
15:40:16     7 be/4 root        0.00 B/s    0.00 B/s  0.00 % 99.99 % [ksoftirqd/0]
15:40:17     7 be/4 root        0.00 B/s    0.00 B/s  0.00 % 99.99 % [ksoftirqd/0]
and so on

How could I disable this?

Thanks in advance,
Peter