[Samba] Samba 3 write performance drop on files > 16 MB

[Jeremy Allison]

On Sat, May 22, 2004 at 10:40:48AM -0400, DKrause at jw.org wrote:
> > I have been running performance tests on our Debian-Samba 3 file
> > server.  It is running the 2.4 kernel on a ProLiant DL380 G3 server
> > (Full Specs below).  For a windows client, we are running Windows 2003
> > server on the exact same hardware.  They are both running at Gigabit
> > speed.  
> > 
> > What we have found is that on files 16MB and smaller we can get better
> > performance Windows client to Linux Server through SMB than we can get
> > Windows to local disk.  (Both servers have the same disk subsystem)
> > We get around 120,000KB/sec throughput.  But after 16MB, the
> > performance drops until it flatlines from 32MB on at 5000 to
> > 7000KB/sec throughput.  This drop does not occur on either server
> > running the tests locally, which shows the drop is not due to memory
> > caching or controller caching.  Additionally, SMB reads stay constant
> > at around 50 to 60,000KB per second.
> > I ran ethereal and found one surprising difference between the 16MB
> > and 32MB transfers.  For approximately .8 seconds before the transfer
> > begins, the following conversation occurs over and over:
> > 
> > Windows>Linux Write AndX Request
> > Linux>Windows Write AndX Response
> > Windows>Linux Trans2 Request, QUERY_FILE_INFO, FID: 0x212a, Query File
> > Standard Info
> > Linux>Windows Trans2 Response, QUERY_FILE_INFO
> > 
> > I have tried all of the recommended SAMBA performance tweaks that I
> > can find, but none seem to affect this dropoff.  Has anyone seen this?
> > It appears to be a bug in either Samba or Windows 2003.

Have you tried this against a W2K3 server ? If it behaves
the same way then it's a client issue, if not we need to
examine how Samba differs.

Jeremy.