Tuning SMB

Making a Samba server "very fast" involves moving from standard compatibility settings to performance-focused ones.

Important Warning: "Fast" is relative to your hardware. The settings below assume you have decent hardware (Gigabit or 10-Gigabit Ethernet and modern hard drives or SSDs).

Here is the step-by-step tuning guide, ordered from "Safe & Effective" to "Advanced."

Step 1: The "Turbo" Config (Safe & Effective)

Modern Samba relies on Asynchronous I/O (AIO) and Multichannel support.

1. Open your config:

   Bash

    sudo nano /etc/samba/smb.conf
   

2. Add the following lines inside the [global] section. (Remove any conflicting lines if you see them).

   Ini, TOML

    [global]
    # ... existing settings ...
   
    # 1. Enable Asynchronous I/O (Crucial for speed)
    # This forces Samba to handle reads/writes without blocking the CPU.
    aio read size = 1
    aio write size = 1
   
    # 2. Network Optimization
    # TCP_NODELAY sends data immediately without waiting for full packets.
    # Note: Do NOT set SO_RCVBUF or SO_SNDBUF manually anymore; Linux auto-tunes this better than you can.
    socket options = TCP_NODELAY IPTOS_LOWDELAY
   
    # 3. Enable SMB Multichannel (The "Turbo Button")
    # Allows a single client to use multiple network connections simultaneously.
    # Tremendously increases throughput if you have dual LAN ports or fast WiFi + LAN.
    server multi channel support = yes
   
    # 4. Apple/Mac Optimizations (If you use Macs)
    # Makes browsing folders on macOS much snappier.
    vfs objects = fruit streams_xattr
    fruit:metadata = stream
    fruit:model = MacSamba
    fruit:posix_rename = yes
    fruit:veto_appledouble = no
    fruit:nfs_aces = no
    fruit:wipe_intentionally_left_blank_rfork = yes
    fruit:delete_empty_adfiles = yes
   
    # 5. General Speed Tweaks
    use sendfile = yes
    min receivefile size = 16384
    getwd cache = yes
   

3. Save and restart Samba:

   Bash

    sudo systemctl restart smbd
   

---

Step 2: Enable "Jumbo Frames" (The Network Layer)

If you are transferring large files (movies, backups) over a wired connection, standard network packets are too small (1500 bytes). Increasing this to 9000 bytes (Jumbo Frames) significantly reduces CPU load and increases speed.

Prerequisite: Your Router/Switch AND your PC must also support/be set to Jumbo Frames (MTU 9000). If one device doesn't support it, the connection will break.

1. Check current MTU:

   Bash

    ip link show
    # Look for "mtu 1500"
   

2. Set MTU to 9000 (Temporary Test):

   Bash

    sudo ip link set dev eth0 mtu 9000
    # (Replace 'eth0' with your actual interface name, e.g., enp3s0)
   

3. Test the transfer. If it works and is faster, make it permanent in your Netplan or NetworkManager settings.

---

Step 3: Hardware Reality Check

If you apply all the settings above and it's still slow, the bottleneck is physical.

• HDD vs. SSD: If you are using mechanical hard drives, you are capped at roughly 100MB/s - 150MB/s. No software tuning can fix this. You need an SSD or a RAID array.

• WiFi vs. Ethernet: WiFi (even WiFi 6) is terrible for sustained file transfer protocols like SMB due to latency. Always test speed over a CAT6 cable.

• CPU Power: Samba is single-threaded per user connection (unless Multichannel is active). If you have a very weak CPU (like an old Raspberry Pi), it might max out at 30-40MB/s regardless of your disk speed.