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

On Fri, Aug 18, 2023 at 04:25:28PM +0000, Jones Syue ???
wrote:
>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
OH - that's *really* interesting ! I wonder how it is
changing the SMB3+ redirector to do this ?

Hello Jeremy,
> 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,
(https://learn.microsoft.com/en-us/sysinternals/downloads/procmon)
this is a example for writing, using applications (Fastcopy.exe, 
explorer.exe, and robocopy.exe) to transfer a file named '1GB.img' from 
local disk 'H:' to remote SMB mount disk 'Z', 
and monitor them with procmon: 

1. FastCopy (FastCopy.exe), 8MB (need to revise FastCopy default setup)
Process Name	Operation	Path	Detail
System	TCP Send	10.19.7.63:64845 -> 10.19.250.98:445	Length: 8388724,
startime: 3459115, endtime: 3459149, seqnum: 0, connid: 0
System	TCP Receive	10.19.7.63:64845 -> 10.19.250.98:445	Length: 84, seqnum:
0, connid: 0
FastCopy.exe	WriteFile	\\10.19.250.98\Public\1GB.img	Offset: 92,274,688, Length:
8,388,608, Priority: Normal

2. File Explorer (explorer.exe), 1MB, drag-and-drop files.
Process Name	Operation	Path	Detail
explorer.exe	ReadFile	H:\1GB.img	Offset: 55,574,528, Length: 1,048,576,
Priority: Normal
System	ReadFile	H:\1GB.img	Offset: 55,574,528, Length: 1,048,576, I/O Flags:
Non-cached, Paging I/O, Priority: Normal
System	WriteFile	\\10.19.250.98\Public\1GB.img	Offset: 55,574,528, Length:
1,048,576, Priority: Normal
System	TCP Send	10.19.7.63:64845 -> 10.19.250.98:445	Length: 1048692,
startime: 3545682, endtime: 3545689, seqnum: 0, connid: 0
System	TCP Receive	10.19.7.63:64845 -> 10.19.250.98:445	Length: 84, seqnum:
0, connid: 0

3. robocopy (robocopy.exe), 1MB, command 'robocopy.exe h: z: 1GB.img
/NP'
Process Name	Operation	Path	Detail
Robocopy.exe	ReadFile	H:\1GB.img	Offset: 520,093,696, Length: 1,048,576,
Priority: Normal
System	WriteFile	\\10.19.250.98\Public\1GB.img	Offset: 520,093,696, Length:
1,048,576, Priority: Normal
System	TCP Send	10.19.7.63:64845 -> 10.19.250.98:445	Length: 1048692,
startime: 3618938, endtime: 3618945, seqnum: 0, connid: 0
System	TCP Receive	10.19.7.63:64845 -> 10.19.250.98:445	Length: 84, seqnum:
0, connid: 0

Perhaps i could do 'procmon' with other benchmark tool like iometer,
get back here later :)

Found a video talking about SMB2 redirector and large I/O size,
thouhd it is not up-to-date SMB3+ redirector still good to know about 
related design thoughts in the history:
https://learn.microsoft.com/en-us/events/pdc-pdc08/es23
0:15:46 SMB2 Redirector
0:17:13 CopyFile API, 1MB I/O request
0:22:46 Application Guidelines


--

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