[Samba] Samba process throttled back?

[Jeremy Allison]

On Fri, Jun 17, 2011 at 09:39:16AM -0400, Lang, Rich wrote:
> Hello,
> 
> We are running Samba 3.0.33 on a 2-node Linux cluster running RedHat 5.6 ES.  Its primary application is to serve out a single network drive to support our business (out 350GB in size).  For several years, this solution has been running flawlessly.  File access was almost as fast as a local disk, so putting files on the server was never a problem.  Our clients are running mostly Windows XP Pro.  We have a few Windows 7 clients.
> 
> Almost a year ago, that changed.  Applications written in VB 6.0 that read files from the server started showing *significant* performance problems.  What used to take seconds now takes more than a minute to finish.  Moving the file to a local disk brought the speed back up to where it should be.  Moving the file to a Windows 2003 or 2008 server also provided good throughput.  All clients experience this same problem.
> 
> I ran "strace -f" against the smbd process that is assigned to my desktop and then ran the VB application to see what the daemon was up to.  I discovered that it went through a process of opening the file several times and reading data from it, using progressively smaller buffer sizes until is settled on using a buffer size of 1, which it used for the remainder of the file I/O session.

This *seems* like clients not using oplocks, when previously
they were. Has anything changed in the server system that might
be denying oplock requests ?

Jeremy.