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

[DKrause at jw.org]

I tried W2K3 to W2K3 server, still on same hardware.  It does not get as
high of performance initially, but it also does not drop off after 16MB.
It stayed at about 25 to 30,000KB/sec.

-----Original Message-----
From: Jeremy Allison [mailto:jra at samba.org] 
Sent: Monday, May 24, 2004 11:49 AM
To: Krause, David
Cc: samba at lists.samba.org
Subject: Re: [Samba] Samba 3 write performance drop on files > 16 MB


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.