Backup Central

Hello,

I know that this is not exactly related to Bacula, but maybe some
other user has seen similar behaviour.

I have problems when trying to enable support for jumbo frames on the
network. All NICs and switches are supposed to support that, however
on some systems the communication of the FD to the SD stops as soon as
I change on the FD the MTU from the default of 1500 to a higher value
(9000). The MTU on the DIR and SD can be set to 9000 without visible
impact on bacula.

Funny thing is that this happens not on all systems.

Does this ring a bell somewhere?

Thanks in advance.

Best regards,

Wolfgang Denk

--
DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd < at > denx.de
This restaurant was advertising breakfast any time. So I ordered
french toast in the renaissance. - Steven Wright, comedian

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Some Network card are supposed to "support" Jumbo frames but not as high value as 9000 octets.
I remember I had issues with some broadcom NIC that couldn't go further than 7200.
Maybe you could take a look at the NIC on the impacted hosts

regards

Le 06/01/2012 17:30, Wolfgang Denk a écrit : Hello,

I know that this is not exactly related to Bacula, but maybe some
other user has seen similar behaviour.

I have problems when trying to enable support for jumbo frames on the
network. All NICs and switches are supposed to support that, however
on some systems the communication of the FD to the SD stops as soon as
I change on the FD the MTU from the default of 1500 to a higher value
(9000). The MTU on the DIR and SD can be set to 9000 without visible
impact on bacula.

Funny thing is that this happens not on all systems.

Does this ring a bell somewhere?

Thanks in advance.

Best regards,

Wolfgang Denk


--
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. --> [/url]
Alexandre Chapellon
Ingénierie des systèmes open sources et réseaux.
Follow me on twitter: [url=http://www.twitter.com/alxgomz] < at > alxgomz

On 01/06/12 11:30, Wolfgang Denk wrote:
Hello,

I know that this is not exactly related to Bacula, but maybe some
other user has seen similar behaviour.

I have problems when trying to enable support for jumbo frames on the
network. All NICs and switches are supposed to support that, however
on some systems the communication of the FD to the SD stops as soon as
I change on the FD the MTU from the default of 1500 to a higher value
(9000). The MTU on the DIR and SD can be set to 9000 without visible
impact on bacula.

Funny thing is that this happens not on all systems.

Does this ring a bell somewhere?

Thanks in advance.

Best regards,

Wolfgang Denk


Hi Wolfgang

I have only seen issues like this when some device along the path is not
properly supporting jumbo frames.

Sometimes a device will require a reboot to make the jumbo frames setting take
affect. I have seen this with DELL switches, for instance.

A quick (non-bacula) way to test is to ssh from one machine to the other and
run a find / command or something that will generate similar amount of output.
If jumbo frames are not enabled on the whole path, then this output will
appear to "just hang" and you will no longer have connectivity to the system.

It is also possible that some of the NICs in your servers are not properly
supporting the higher MTU that you are setting.

Hope this helps.

--
Bill Arlofski
Reverse Polarity, LLC

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On 01/06/2012 11:30 AM, Wolfgang Denk wrote:
Hello,

I know that this is not exactly related to Bacula, but maybe some
other user has seen similar behaviour.

I have problems when trying to enable support for jumbo frames on the
network. All NICs and switches are supposed to support that, however
on some systems the communication of the FD to the SD stops as soon as
I change on the FD the MTU from the default of 1500 to a higher value
(9000). The MTU on the DIR and SD can be set to 9000 without visible
impact on bacula.

Are all of the machines on the same subnet? If not, you'll also have to check
the MTU on all of your local router interfaces.

--
Frank Sweetser fs at wpi.edu | For every problem, there is a solution that
Manager of Network Operations | is simple, elegant, and wrong.
Worcester Polytechnic Institute | - HL Mencken

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costs. Try it free! http://p.sf.net/sfu/Citrix-VDIinabox
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On 01/06/12 11:55, Alexandre Chapellon wrote:
Some Network card are supposed to "support" Jumbo frames but not as high
value as 9000 octets.
I remember I had issues with some broadcom NIC that couldn't go further
than 7200.
Maybe you could take a look at the NIC on the impacted hosts

That. Before enabling jumbo frames on ANY network link, test from both
ends with MTU steps from about 4000 or so to 9000 in steps of 500 to
1000 (smaller, if you're patient) to make sure that both NICs *AND THEIR
DRIVERS* actually support jumbo frames, and find out what maximum MTU
they support. I bought a D-Link 24-port gigabit switch that supports
jumbo frames up to about MTU 9400, specifically to get jumbo frame
support, and only then, when I could actually test, found out that
neither the Solaris 10 bcm driver for the Broadcom GigE ports on my
server, nor the Linux forcedeth driver for the nVidia MCP77 GigE port on
my workstation, support jumbo frames.

Needless to say, I was annoyed.


--
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alaric < at > caerllewys.net alaric < at > metrocast.net phil < at > co.ordinate.org
Renaissance Man, Unix ronin, Perl hacker, SQL wrangler, Free Stater
It's not the years, it's the mileage.

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infrastructure or vast IT resources to deliver seamless, secure access to
virtual desktops. With this all-in-one solution, easily deploy virtual
desktops for less than the cost of PCs and save 60% on VDI infrastructure
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Hi,

You can use ping to check the end-to-end maximum MTU working size:

ping -Mdo -s 8000 192.168.X.X

increase or reduce the size (8000) until you get pings back from the FD client (mine goes up to 8972)

Pablo
----- Original Message -----
From: "Frank Sweetser" <fs < at > WPI.EDU>
To: bacula-users < at > lists.sourceforge.net
Sent: Friday, January 6, 2012 11:34:44 AM
Subject: Re: [Bacula-users] Problems with Jumbo packets?

On 01/06/2012 11:30 AM, Wolfgang Denk wrote:
Hello,

I know that this is not exactly related to Bacula, but maybe some
other user has seen similar behaviour.

I have problems when trying to enable support for jumbo frames on the
network. All NICs and switches are supposed to support that, however
on some systems the communication of the FD to the SD stops as soon as
I change on the FD the MTU from the default of 1500 to a higher value
(9000). The MTU on the DIR and SD can be set to 9000 without visible
impact on bacula.

Are all of the machines on the same subnet? If not, you'll also have to check
the MTU on all of your local router interfaces.

Bacula-users mailing list
Bacula-users < at > lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/bacula-users

------------------------------------------------------------------------------
Ridiculously easy VDI. With Citrix VDI-in-a-Box, you don't need a complex
infrastructure or vast IT resources to deliver seamless, secure access to
virtual desktops. With this all-in-one solution, easily deploy virtual
desktops for less than the cost of PCs and save 60% on VDI infrastructure
costs. Try it free! http://p.sf.net/sfu/Citrix-VDIinabox
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Dear Alexandre,

In message <4F072790.9060505 < at > horoa.net> you wrote:

Some Network card are supposed to "support" Jumbo frames but not as high
value as 9000 octets.
I remember I had issues with some broadcom NIC that couldn't go further
than 7200.
Maybe you could take a look at the NIC on the impacted hosts

Yes, I do have some of these, too. But these are easy to spot as they
don't accept larger MTU's:

# ifconfig eth0 mtu 9000
SIOCSIFMTU: Invalid argument
# ifconfig eth0 mtu 7200
#

Best regards,

Wolfgang Denk

--
DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd < at > denx.de
Applying computer technology is simply finding the right wrench to
pound in the correct screw.

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infrastructure or vast IT resources to deliver seamless, secure access to
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costs. Try it free! http://p.sf.net/sfu/Citrix-VDIinabox
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Dear Frank Sweetser,

In message <4F0722A4.5090307 < at > wpi.edu> you wrote:

Are all of the machines on the same subnet? If not, you'll also have to check
the MTU on all of your local router interfaces.

Yes, they are all in the same net, and all on the same switch.

Best regards,

Wolfgang Denk

--
DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd < at > denx.de
Quote from the Boss after overriding the decision of a task force he
created to find a solution: "I'm sorry if I ever gave you the
impression your input would have any effect on my decision for the
outcome of this project!"

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Dear Bill,

In message <4F0728E7.7050103 < at > revpol.com> you wrote:

A quick (non-bacula) way to test is to ssh from one machine to the other and
run a find / command or something that will generate similar amount of output.
If jumbo frames are not enabled on the whole path, then this output will
appear to "just hang" and you will no longer have connectivity to the system.

It is also possible that some of the NICs in your servers are not properly
supporting the higher MTU that you are setting.

Indeed it appears I have to look deeper into the NIC / driver side of
things.

Thanks for all the advice.

Best regards,

Wolfgang Denk

--
DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd < at > denx.de
An expert is a person who avoids the small errors while sweeping on
to the grand fallacy.

------------------------------------------------------------------------------
Ridiculously easy VDI. With Citrix VDI-in-a-Box, you don't need a complex
infrastructure or vast IT resources to deliver seamless, secure access to
virtual desktops. With this all-in-one solution, easily deploy virtual
desktops for less than the cost of PCs and save 60% on VDI infrastructure
costs. Try it free! http://p.sf.net/sfu/Citrix-VDIinabox
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