samba - Oct 2011 - Strange Performance Issue / concurrent clients -> very very slow

Hi,

recently I installed a new GBit connected iSCSI Storage to one of our
fileservers. Redhat EL Linux 5.7 samba3x-3.5.4-0.83.el5, kernel
2.6.18-238.19.1.el5PAE, Dell Poweredge 1750, dual Xeon.

The transfer speed is very very different, depending on the method I
use. Currently I'm the only user accessing that server and there is low
network traffic.

I know, that there are some overheads etc. which influence the speed.

My Test Client is a Macbook pro  and a Mac Pro (OS X 10.6.x each,
connected by GBit wired lan)

I copy a couple of 30 MB files and in an other test files of 1GB.

Transferspeed for ftp is about 85 MB/s, scp about 25 MB/s, samba 30 MB/s.

So the 'raw' speed is o.k. for me, more that 30 MB would be nice.

BUT the most confusing thing is, as soon as I copy files from two
clients at the same time to my samba share, the performance drops to 5
MB/s for each client. So 10 MB/s.

Transferring from two ftp clients is about 40 MB/s per client.

Currently I use 'socket options = TCP_NODELAY SO_RCVBUF=8192
SO_SNDBUF=8192 IPTOS_LOWDELAY'

Dose anybody has an explanation for such a poor performance? Any tunig
tips or hints? Everything is welcome.

	Thanks and best regards. G?tz

-- 
G?tz Reinicke
IT-Koordinator

Tel. +49 7141 969 420
Fax  +49 7141 969 55 420
E-Mail goetz.reinicke at filmakademie.de

Filmakademie Baden-W?rttemberg GmbH
Akademiehof 10
71638 Ludwigsburg
www.filmakademie.de

Eintragung Amtsgericht Stuttgart HRB 205016

Vorsitzender des Aufsichtsrats:
J?rgen Walter MdL
Staatssekret?r im Ministerium f?r Wissenschaft,
Forschung und Kunst Baden-W?rttemberg

Gesch?ftsf?hrer:
Prof. Thomas Schadt

Is the new GBit iSCSI storage connected on the same collision domain 
as the other machines?

  If so, you may be hitting the limit of the switch. Try separating 
iSCSI from the rest of the network with another switch, or at least a 
separate VLAN.

Greetings

  Jos?

On 10/28/2011 10:04 AM, G?tz Reinicke wrote:
> Hi,
>
> recently I installed a new GBit connected iSCSI Storage to one of our
> fileservers. Redhat EL Linux 5.7 samba3x-3.5.4-0.83.el5, kernel
> 2.6.18-238.19.1.el5PAE, Dell Poweredge 1750, dual Xeon.
>
> The transfer speed is very very different, depending on the method I
> use. Currently I'm the only user accessing that server and there is low
> network traffic.
>
> I know, that there are some overheads etc. which influence the speed.
>
> My Test Client is a Macbook pro  and a Mac Pro (OS X 10.6.x each,
> connected by GBit wired lan)
>
> I copy a couple of 30 MB files and in an other test files of 1GB.
>
> Transferspeed for ftp is about 85 MB/s, scp about 25 MB/s, samba 30 MB/s.
>
> So the 'raw' speed is o.k. for me, more that 30 MB would be nice.
>
> BUT the most confusing thing is, as soon as I copy files from two
> clients at the same time to my samba share, the performance drops to 5
> MB/s for each client. So 10 MB/s.
>
> Transferring from two ftp clients is about 40 MB/s per client.
>
> Currently I use 'socket options = TCP_NODELAY SO_RCVBUF=8192
> SO_SNDBUF=8192 IPTOS_LOWDELAY'
>
> Dose anybody has an explanation for such a poor performance? Any tunig
> tips or hints? Everything is welcome.
>
> 	Thanks and best regards. G?tz
>
>
>

On Fri, Oct 28, 2011 at 05:04:37PM +0200, G?tz Reinicke
wrote:
> 
> Currently I use 'socket options = TCP_NODELAY SO_RCVBUF=8192
> SO_SNDBUF=8192 IPTOS_LOWDELAY'
Remove this line. Setting "socket options" on a modern Linux
kernel is like shaking a chicken at the machine (or SCSI
termination magic). Let the kernel self-tune these variables
and you'll be much happier.

Jeremy.