[Samba] Speed differences for windows clients

Jeff Layton jlayton at redhat.com
Tue Aug 13 17:53:38 MDT 2013

On Mon, 12 Aug 2013 10:00:18 +0200
Philipp Lies <philipp.lies at cin.uni-tuebingen.de> wrote:

> Hi,
> we have a strange phenomenon with the transfer speed between windows 
> clients and samba servers. Here's the setup:
> server 1: centos 6.3 with samba 3.5.10
> server 2: centos 6.4 with samba 3.6.9
> both servers are configured as BDC and have - aside from netbios name - 
> identical smb.conf which contains ldapsam as backend and all other 
> parameters are not set (i.e. default)
> When I mount a share from a linux client, the transfer speed is 
> ~112MB/sec to either server from any linux client. However, when I mount 
> a share from Windows clients, the speed to server 1 is ~95MB/s and to 
> server 2 ~85MB/s. We tested this with several windows clients (all 
> running Windows 7 with all updates).
> The speed difference between linux client and windows client is not 
> what's confusing me but that server 2 is always slower than server 1.
> Any ideas what could cause this?
> Philipp

The speed difference between Linux and Windows clients is most likely
explained by the fact that Linux clients will almost always negotiate
POSIX extensions with the server. At that point, they're allowed to
bump up the rsize/wsize values to much larger values. Newer kernels
will default to 1M for both. That greatly increases throughput.

As far as the difference between the two servers from windows clients,
it'll be difficult to be sure without doing some more legwork to track
down the cause.

Jeff Layton <jlayton at redhat.com>

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