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

Jeremy Allison jra at samba.org
Mon Aug 21 20:55:44 UTC 2023

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 wonder if setting a CreateOptions allows this
somehow ?

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