[Samba] Increase data length for SMB2 write and read requests for Windows 10 clients

Ralph Boehme slow at samba.org
Tue Aug 22 06:50:03 UTC 2023

On 8/21/23 22:55, Jeremy Allison wrote:
> On Mon, Aug 21, 2023 at 03:19:59PM +0200, Ralph Boehme wrote:
>> On 8/21/23 11:53, Jones Syue 薛懷宗 via samba wrote:
>>>> OH - that's *really* interesting ! I wonder how it is
>>>> changing the SMB3+ redirector to do this ?
>>> It looks like applications could do something and give a hint to SMB3+
>>> redirector, so far not quite sure how to make it,
>>> per process monitor (procmon) could show that write I/O size seems
>>> could be pass from the application layers,
>> well, sure, the application layer drives IO with the IO size it 
>> chooses. But when the application layer issues IOs larger then the 
>> maximum IO size allowed by SMB (8 MB iirc), the Windows SMB kernel 
>> client will segment the larger application segments into smaller ones.
> Fastcopy is doing *something* weird :-).
> 1. FastCopy (FastCopy.exe), 8MB (need to revise FastCopy default setup)
> Process Name    Operation       Path    Detail
> System  TCP Send ->    Length: 
> 8388724, startime: 3459115, endtime: 3459149, seqnum: 0, connid: 0
> System  TCP Receive ->    Length: 
> 84, seqnum: 0, connid: 0
> FastCopy.exe    WriteFile       \\\Public\1GB.img   Offset: 
> 92,274,688, Length: 8,388,608, Priority: Normal
> I wonder if it has it's own SMB client code
> built in ?
> Either that or it knows what parameters to change
> in the SMB redirector to request 8MB IO.

I don't get it. Iirc 8 MB is the default max io size the kernel client 
will use which is also, iirc, the limit of the protocol.


Ralph Boehme, Samba Team                      https://samba.org/
SerNet Samba Team Lead                     https://sernet.de/en/
LinkedIn  https://www.linkedin.com/in/ralph-b%C3%B6hme-43917162/
SAMBA+ Samba packages                        https://samba.plus/
SAMBA+ AIX Webinar             https://samba.plus/samba-webinars

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