[Samba] Samba ignoring socket options?

Mike Myers mikesm559 at yahoo.com
Fri Aug 29 17:30:42 GMT 2008

I still see the problem.  I don't have another real linux system to test, but will install another copy on a different system and configure it for dual boot.  I can't really do that easily on on the same hardware as the existing windows machines with raid, since there is no non-raid boot partition on those.  I do have a laptop and some other machines that I can do dual-boot on, but I am concerned that the local filesystem will be a bottleneck as it's just a single disk.  My experience is that you really can't test the maxmium speed for a server with a fast raid configuration to a client that has a non-raid disk - the local target for the file just can't keep up, but it may be able to go faster than 30 MB/s...

It may take me another day or so to ready such a configuration for test.

I will go ahead and set up a new samba share off the system disk which isn't part of the raid5 sets, and uses resierfs and try that too. The disk I use should be able to do north of 60 MB/s in raw transfer rate on sequential reads, so if resier doesn't get too much in the way, it should be able to supply samba at a rate of more than the 30 MB/s I see for transfers off the raid volume.

I am still curious as to why changing the socket buffer settings to a wide variety of options has absolutely no effect on perfromance.  Steve Thompson seems to have noticed the same issue, and my experience tells me that if I set the SO_SNDBUF and SO_RCVBUF to something like 512 on an app, that it slaughters performance.  It certainly does for netperf, so I can't understand if Samba is really using those options why setting it to 512 doesn't slow the speed down like it does for netperf.  

I don't mean to be presumptuous, but these data points re: no speed variance even in the face of tiny buffer settings indicates that something is wrong with the options being exercised, so I am curious as to why you think the options are being used?  Jeremy and Lars, in your test environment, can you try setting the SO_SNDBUF and SO_RCVBUF down to 512 and see if you also do not notice a variance in performance?

Thanks much,

----- Original Message ----
From: Lars Müller <lmuelle at suse.de>
To: Mike Myers <mikesm559 at yahoo.com>
Cc: samba at lists.samba.org
Sent: Friday, August 29, 2008 4:36:30 AM
Subject: Re: [Samba] Samba ignoring socket options?

On Thu, Aug 28, 2008 at 12:53:00PM -0700, Mike Myers wrote:
> Hi everyone.  I am running Samba 3.2.0-22.1 (as packaged by OpenSUSE in
> 11.0) on a storage server connected to multiple windows based clients
> over a gigabit ethernet link.  The server is a quad core Intel CPU and
> is equipped with an Intel e1000 based gigabit ethernet controller and plugged into a common gigabit ethernet switch with the windows clients.

Is this still the case?

In addition to Jeremy's suggestion I'd like to see you testing this with
a straight connection between the two systems.  But after reading the
rest of your posting it's not very liekly to help.

For openSUSE 11.0 we'll also soon see an official update to 3.2.3.

Meanwhile you might use the packages provided by the openSUSE Build
Service.  See http://en.opensuse.org/Samba#openSUSE_Build_Service for
how to access them.

> Samba is getting roughly 30 MB/s tranfer rates from the linux server to a windows vista and a windows XP client,
> and the disks on both windows machines are RAID0 (4 and 2 disk RAID0
> sets respectively), so I don't think I am running into filesystem
> performance issues on the target.  Moving from the windows systems to Samba, I see about 45 MB/sec transfers rates.

The write case is faster than read.  Strange to me.

> The
> raid array on the samba server consist of 2 6 disk raid5 sets with fast
> disks on them, running lvm and XFS for a filesysteem.  I can do a dd of
> a multigigabyte file to /dev/null and get roughly 500-600 MB/'s
> transfer rates through the filesystem, so I don't think the raid array
> and file system is a bottleneck.

Do you have some space on a local disk with ext2, no raid, no lvm?  Only
to ensure your issue isn't caused by one of these components.

> I have run netperf tests
> between the server and the clients to see if I had some network
> plumbing problems.  With default socket settings for netperf (8182
> buffer size), I get about 300 mbps transfer rates between the clients
> and the server (which matches approximately the 30 MB/s transfer
> rates).  With 65536 byte buffers, that number goes to 970 or so Mbps,
> so I think the interface cards, TCP stack, switches are all ok.

Therefore this might be caused by the file system in use.  Please try to
test the way as suggested above.  If it isn't solved already.

Lars Müller [ˈlaː(r)z ˈmʏlɐ]
Samba Team
SUSE Linux, Maxfeldstraße 5, 90409 Nürnberg, Germany


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