samba - Sep 2025 - How to speed up small file writes? (WSL2 / Windows)

Test data with 7633 scrambled emails, i.e. many small files:

https://files.f76.eu/samba/2025-09-10+08_test.tgz

Setup:

  * SMB Guest: Windows 11 Pro x64

  * SMB Host: Ubuntu running in Linux WSL2 in the above Windows

=> Host and Guest are running on the same hardware. Networking should be
fast.

My tests:

 1. Extract the archive on Linux in a local EXT4 mount. That takes less
    than eight seconds:

        [felix at felix-x1t3-11 test]$ time tar xfz 2025-09-10+08_test.tgz

        real    0m7.592s
        user    0m6.114s
        sys     0m3.590s

 2. Extract the archive on Windows in a local NTFS mount. That takes
    less than sixteen seconds:

        PS C:\Users\Felix\Desktop\test> Measure-Command {
        >> tar xfz .\2025-09-10+08_test.tgz
        >> }


        Days              : 0
        Hours             : 0
        Minutes           : 0
        Seconds           : 15
        Milliseconds      : 995
        Ticks             : 159958396
        TotalDays         : 0.000185137032407407
        TotalHours        : 0.00444328877777778
        TotalMinutes      : 0.266597326666667
        TotalSeconds      : 15.9958396
        TotalMilliseconds : 15995.8396

 3. Extract the archive on Windows in the Linux directory from step 1,
    mounted by SMB. That takes more than 176 seconds:

        PS Microsoft.PowerShell.Core\FileSystem::\\172.18.61.229\share\
        test> Measure-Command {
        >> tar xfz .\2025-09-10+08_test.tgz
        >> }


        Days              : 0
        Hours             : 0
        Minutes           : 2
        Seconds           : 56
        Milliseconds      : 254
        Ticks             : 1762546126
        TotalDays         : 0.00203998394212963
        TotalHours        : 0.0489596146111111
        TotalMinutes      : 2.93757687666667
        TotalSeconds      : 176.2546126
        TotalMilliseconds : 176254.6126

=> Access via Samba is 11 to 22 times slower than native access. It?s
basically unusably slow. I wonder if something can be done to improve
the speed.

I know WSL2 has built-in cross-platform file access via 9P. However,
performance there is not great either, and eventually I would like to
migrate from WSL2 to Linux in Hyper-V. NFS would be an alternative to
Samba, but an earlier test showed very bad small file performance as
well.

Additional details:

  * `smbd  --version`:

        Version 4.21.4-Ubuntu-4.21.4+dfsg-1ubuntu3.4

  * `/etc/samba/smb.conf`:

        [global]
           workgroup = WORKGROUP
           security  = user
           map to guest = Bad User
           load printers = no
           disable spoolss = yes
           strict locking = no
           use sendfile = yes
           min receivefile size = 128k
           socket options = IPTOS_LOWDELAY TCP_NODELAY
           oplocks = yes
           aio read size = 1
           aio write size = 1
           kernel oplocks = no
           host msdfs = no
           strict sync = no

        [share]
           path = /home/felix/tmp
           read only = no
           browseable = yes
           force user = felix
           create mask = 0644
           directory mask = 0755

On 10.09.2025 15:25, Felix E. Klee via samba wrote:
> Test data with 7633 scrambled emails, i.e. many small files:
> 
> https://files.f76.eu/samba/2025-09-10+08_test.tgz
> 
> Setup:
> 
>    * SMB Guest: Windows 11 Pro x64
> 
>    * SMB Host: Ubuntu running in Linux WSL2 in the above Windows
> 
> => Host and Guest are running on the same hardware. Networking should be
> fast.
> 
> My tests:
> 
>   1. Extract the archive on Linux in a local EXT4 mount. That takes less
>      than eight seconds:
> 
>          [felix at felix-x1t3-11 test]$ time tar xfz 2025-09-10+08_test.tgz
> 
>          real    0m7.592s
>          user    0m6.114s
>          sys     0m3.590s
> 
>   2. Extract the archive on Windows in a local NTFS mount. That takes
>      less than sixteen seconds:
> 
>          PS C:\Users\Felix\Desktop\test> Measure-Command {
>          >> tar xfz .\2025-09-10+08_test.tgz
>          >> }
> 
> 
>          Days              : 0
>          Hours             : 0
>          Minutes           : 0
>          Seconds           : 15
>          Milliseconds      : 995
>          Ticks             : 159958396
>          TotalDays         : 0.000185137032407407
>          TotalHours        : 0.00444328877777778
>          TotalMinutes      : 0.266597326666667
>          TotalSeconds      : 15.9958396
>          TotalMilliseconds : 15995.8396
> 
>   3. Extract the archive on Windows in the Linux directory from step 1,
>      mounted by SMB. That takes more than 176 seconds:
> 
>          PS Microsoft.PowerShell.Core\FileSystem::\\172.18.61.229\share\
>          test> Measure-Command {
>          >> tar xfz .\2025-09-10+08_test.tgz
>          >> }
> 
> 
>          Days              : 0
>          Hours             : 0
>          Minutes           : 2
>          Seconds           : 56
>          Milliseconds      : 254
>          Ticks             : 1762546126
>          TotalDays         : 0.00203998394212963
>          TotalHours        : 0.0489596146111111
>          TotalMinutes      : 2.93757687666667
>          TotalSeconds      : 176.2546126
>          TotalMilliseconds : 176254.6126
> 
> => Access via Samba is 11 to 22 times slower than native access. It?s
> basically unusably slow. I wonder if something can be done to improve
> the speed.
Please also do another test: windows to a network drive which
is run by another windows machine (I dunno if you can do this on
a single machine though).

When I have to copy large amount of files from one windows machine
to another, I usually do it using intermediate tar archive - creating
such archive locally, next reading it from another machine extracting
there.  So it is just one open across network, instead of multiple
opens/closes.  Or else an operation which - with the help of temorary
tar archive like this - increases from several minutes to multiple
hours.

That to say: windows networking is slow when opening files.

Thanks,

/mjt