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

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

On Wed, Sep 10, 2025 at 9:49?PM Michael Tokarev <mjt at tls.msk.ru>
wrote:
> 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).
That?s a great suggestion! It would be possible to test
Windows-to-Windows SMB performance with a Windows VM, but I am too lazy
to set that up right now. What I did, however, is test extraction speed
with the tar file hosted on Windows from Linux:

    root at felix-x1t3-11:/tmp/test# time tar xfz 2025-09-10+08_test.tgz

    real    0m38.990s
    user    0m3.082s
    sys     0m3.037s

I also tried a few more tweaks to the Samba configuration by removing
meta data preservation, see below. With that I can get down to 135
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           : 15
    Milliseconds      : 199
    Ticks             : 1351991956
    TotalDays         : 0.00156480550462963
    TotalHours        : 0.0375553321111111
    TotalMinutes      : 2.25331992666667
    TotalSeconds      : 135.1991956
    TotalMilliseconds : 135199.1956

That?s still 3.5 times slower than in the other direction:

At least for small file writes, the SMB server built into Windows seems
to be considerably faster than Samba!

Next I want to try KSMBD. The goal is to get maximum small file write
speed. No file meta data needs to be preserved.

My current `/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
       smb encrypt = disabled

       ea support = no
       store dos attributes = no
       map archive = no
       nt acl support = no

       durable handles = no
       posix locking = no

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