SuSE 10 and SuSE10w/SP1 install a kernel below 2.6.17. If your kernel
is 2.6.16 or less, then the following kernel tuning variables may help
with TCP performance. Add these to /etc/sysctl.conf and reboot:
net.core.rmem_max = 873200
net.core.wmem_max = 873200
net.ipv4.tcp_rmem = 32768 436600 873200
net.ipv4.tcp_wmem = 8192 436600 873200
Additionally, this may help as well:
Check the maximum size of the receive (RX) buffer:
ethtool -g eth0
Example output:
------------------------------------------------
Pre-set maximums:
RX: 4096
TX: 4096
Current hardware settings:
RX: 256
TX: 256
b. Set the RX buffer to the maximum size:
ethtool -G eth0 rx 4096
c. Make this change permanent by adding the ethtool command to the /
etc/init.d/network startup script for the relevant network intefaces
between the lines that read "esac" and "rc_exit" at the end of the
file, for example:
esac
#added following line to raise rx at boot time
ethtool -G eth0 rx 4096
rc_exit
On Dec 7, 2:01 pm, Kmec <jozef.novik...@seznam.cz> wrote:
> Hi,
> I would like to ask for help with some strange behavior of linux
> iscsi. Situation is as follows: iSCSI SAN Dell Equallogic, SAS 10k RPM
> drives, 4x Broadcom NIC or 4x Intel NIC in Dell R900 server (24 cores,
> 64 GB RAM). It's testing environment where we are trying to measure
> SAN Dell EQL performance.
>
> Totally we are solving 2 different issues:
> 1) In case of running IOmeter test on server running Windows 2008
> server, we are able to get 112 MBps read and 110 MBps write over 1NIC,
> 220 MBps read and 210 MBps over 2 NICs. On SuSE 10 or Centos 66 MBps
> read and 38 MBps write only over one NIC. So I think we can forget
> about finding issues on SAN or switch. Strange is, that with dd or
> hdparm we can get wirespeed. Question is what to do to get same
> numbers from IOmeter on Windows and Linux. We also tried dt tool and
> we get same results as from IOmeter.
> How to continue?
>
> 2) our next problem is multipath. When we configure multipath, over
> one NIC with dd we get 90 MBps read, but over 2 NICs just 80 MBps what
> is strange. On switch and SAN we see that data flow is over both NICs,
> but dd shows still 80 MBps.
>
> I will appreciate any suggestion.
>
> Jozef
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