Optimised smb.conf for Windows clients

These Samba config options have been performing fantastically well for me. It took quite a bit of research to finalise the config you see below, so figured it was worth sharing.

My setup is a Debian server with BTRFS storage, and windows clients. Requirements are:

• Good performance, especially with lots of tiny files, complex directory trees, random writes within files, etc.
• Preservation of all reasonable windows file attributes, such as:
  • Creation date
  • DOS attributes
  • Anything else necessary for standard desktop workload such as steam game library, documents/pictures/etc folders, git, etc.
• Continuing the previous point: It should feel like the server is running Windows - no weird surprises.
• No preservation of anything that allows Windows to behave in unpredictable Windows-like ways - specifically no ACL support.
• Sane Linux filesystem permissions
  • When I browse through my windows files, they should look like a Linux home directory, no weird permissions etc.
  • Everything Windows-specific should be abstracted away into xattrs.
  • Everything should be executable on Windows, but not executable on Linux, as that is the cleanest representation of the platform difference IMO.
• Backup-able with standard Linux tools like tar and borg (xattrs must be enabled!)
• Correct behaviour of BTRFS features such as compression.

Without further ado:

[global]
   socket options = IPTOS_LOWDELAY TCP_NODELAY
   use sendfile = yes
   min protocol = SMB2
   vfs objects = btrfs
   create mask = 644
   acl allow execute always = yes
   store dos attributes = yes
   map readonly = no
   map archive = no
   ea support = no
   nt acl support = no

Options I specifically avoid are:

• SO_RCVBUF=131072 SO_SNDBUF=131072 - specifically recommended to avoid by newer Samba releases.
• case sensitive = yes - breaks too many things, performance improvement is barely noticeable.
• strict allocate = yes - breaks BTRFS compression.

And one final note, I noticed a substantial performance improvement in my use case of SMB when upgrading from Debian 9 to Debian 10, so if you are on a lower Samba version than 4.9, consider upgrading!

2022 Update: Removed various options that seem spurious or even wrong after referring to latest documentation. The defaults are better than they used to be.