[Samba] Samba process throttled back?

Lang, Rich LangR at specsensors.com
Fri Jun 17 07:39:16 MDT 2011


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.

I've attached the smb.conf file for your reading pleasure.  I can attach the strace output file if that would be helpful.

I suspect that something changed on the Windows desktop side to bring this about, since we made no changes to our VB code at all.

Richard G. Lang
Sr. Software Engineer
LangR at specsensors.com<mailto:LangR at specsensors.com>
(330) 659-3312

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