https://forums.freenas.org/index.php?threads/slow-transfer-speeds-via-cifs.39867/

https://forums.freenas.org/index.php?threads/cifs-directory-browsing-slow-try-this.27751/

-–CIFS–Advance mode—-Auxiliary Parameters:————-
store dos attributes = no
map system = no
-———————————————————————-
Jumbo Frame enable
-———————————————————————-
In BSD the CFIS implementation is only single threaded

-———————————————————————-
Omni-OS + Napp-it for great iSCSI and CIFS performance
A multithreaded kernel based alternative to SAMBA is Solaris CIFS in Oracle Solaris, OmniOS or NexentaStor

OmniOS is currently SMB1
Nexenta and Solaris 11.3 is SMB 2.1.
Most feature rich is Solaris 11.3 as it includes real ZFS encryption, SMB 2.1, LZ4 compress and fast sequential resilvering

-———————————————————————-

store dos attributes = no
ea support = no
map archive = no
map hidden = no
map system = no
map readonly = no

2. (and 3.) was probably related to the old switch, which is now replaced. Even home PCs had short interruptions, which should be now gone (it seems so).
4. I deleted this share (wasn’t necessary anymore), but didn’t reset the permissions yet.
1. and 5. done.

Now I get speeds around 110-115MB/s.
But with another PC it is around 75MB/s writing to NAS and 95MB/s reading from NAS.

=====
ea support = no
store dos attributes = no
map archive = no
map hidden = no
map readonly = no
map system = no

1. Disables Samba from using EAs.
2. Tells Samba not to store the DOS attributes (any existing bits that are set are simply abandoned in place in the EAs).
3. Forces all 4 parameters to off/no/unchecked/disabled.

Note: The read-only bit I am mentioning, disabling, then forcing to off is not the standard read-only permissions users may be given to files or folders.