samba - Aug 2023 - Increase data length for SMB2 write and read requests for Windows 10 clients

On Wed, Aug 16, 2023 at 04:02:47PM +0100, Ivan Clayson via samba
wrote:
>Hello,
>
>We are currently running a Linux Samba gateway with a CephFS 
>kernel-client to allow Windows 10 clients to transfer data to and from 
>our Ceph storage cluster. We have been using this in production for a 
>while now quite successfully but we are finding that our Windows 
>clients are having their rates limited to ~1 Gbps despite having 10 
>Gbit interfaces (iperf tests show a 4.18 Gbps network speed). We can 
>achieve far higher transfer rates when using Linux clients by setting 
>the "wsize" and "rsize" mount.cifs options (we find that
8MB works
>well) but we've been unable to find an equivalent option for our 
>Windows clients as there doesn't seem to be an option to specify how 
>much the data will be sent in 1 SMB request.
>
>When inspecting the logs (as well as with Wireshark), we can see that 
>the Linux clients have their read and write data lengths specified by 
>the "wsize" and "rsize" options:
I don't know of any Windows client tuning parameter to set to
increase their r/w sizes (or even to change them in any way).

Any Windows experts on this list who might know a "secret"
registry key ?

Hello Ivan,

'FastCopy' has an option to revise max I/O size and works for SMB :)
it is a tool for file transferring and could be installed to win10,
download here: https://fastcopy.jp/

This is an example for writing, a job would write a file named '1GB.img'
from a local disk 'H:' to a remote SMB mounted net disk 'Z:',
open 'FastCopy' tool and specify several options like:
1. specify 'Source':  H:\1GB.img
2. specify 'DestDir': Z:\
3. go to Option > Main Settings > I/O Setting > I/O unit (MB),
the default value is '1' and changes it to '8'.
4. click button 'Execute' to start file transferring.

Then we could see logs said that write size is 8MB (8388608):
[2023/08/18 23:32:02.418926,  3]
../../source3/smbd/smb2_write.c:219(smb2_write_complete_internal)
  smb2: fnum 4162336292, file 1GB.img, length=8388608 offset=226492416
wrote=8388608
And wireshark said that write size is 8MB (8388608):
SMB2	23414	Write Request Len:8388608 Off:100663296 File: 1GB.img

Another example for reading, just switch the disk letter between Source 
and DestDir:
1. specify 'Source':  Z:\1GB.img
2. specify 'DestDir': H:\
3. click button 'Execute' to start file transferring.

And wireshark said that read size is 8MB (8388608):
SMB2	171	Read Request Len:8388608 Off:260046848 File: 1GB.img

--

Regards,
Jones Syue | ???
QNAP Systems, Inc.