Networker

Re: [Networker] Tuning Network to utilize Jumbo Frames on Gig-Eth ernet.

2004-12-15 15:49:10
Subject: Re: [Networker] Tuning Network to utilize Jumbo Frames on Gig-Eth ernet.
From: Terry Lemons <lemons_terry AT EMC DOT COM>
To: NETWORKER AT LISTMAIL.TEMPLE DOT EDU
Date: Wed, 15 Dec 2004 15:38:13 -0500
Hi David

NetWorker does not have any knobs to control Ethernet settings; you have to
do this outside of NetWorker.  If you do use jumbo frames, make sure that
EVERYTHING in the path between the NetWorker client and the NetWorker
storage node is jumbo frame-capable; otherwise, you'll have even worse
performance than if you weren't using jumbo frames.

If you are using Intel Ethernet adapters, see
http://www.intel.com/network/connectivity/resources/doc_library/tech_brief/K
ey_Performance_Gig.pdf.  This white paper makes the case that Intel's TCP
Segmentation (aka "Large Send Off-load") technology is better than jumbo
frames.  How does it work?  "It reduces the OS burden involved in processing
large files into packets by off-loading this task onto hardware using
specialized silicon on the adapter."

Some Ethernet adapters have TCP offload engines (TOE) onboard, which remove
the very substantial IP processing burden from the host CPU.  TOEs are more
expensive than regular Ethernet adapters (and they should be, for what they
provide).

So, the Intel Gigabit Ethernet adapter gives you some of the benefit of a
TOE (e.g., some network operations done by the adapter, instead of the host
CPU), without the extra cost.  TCP Segmentation doesn't do the functions of
a TOE, of course; but it may provide some of the benefits (decreased CPU
load) in your environment.

Look for features like this in other vendor's products.  I knew the Intel
one, so used it as an illustration here.

Hope this helps.

tl

Terry Lemons
CLARiiON Applications Integration Engineering
EMC²                 
where information lives
 
4400 Computer Drive, MS D239
Westboro MA 01580
Phone: 508 898 7312
Email:  Lemons_Terry AT emc DOT com



-----Original Message-----
From: Legato NetWorker discussion [mailto:NETWORKER AT LISTMAIL.TEMPLE DOT EDU] 
On
Behalf Of Fields, David
Sent: Wednesday, December 15, 2004 3:12 PM
To: NETWORKER AT LISTMAIL.TEMPLE DOT EDU
Subject: [Networker] Tuning Network to utilize Jumbo Frames on Gig-Ethernet.

I haven't been able to find any information in the NetWorker documentation
this subject, so I thought I would ask here.  Does NetWorker automatically
adjust itself to utilize jumbo frames on a gig Ethernet network, or do you
have to tune it somehow to make use out of it?  Also, I've heard it
mentioned a few times on there that you should tune your Ethernet frame size
to your tape frame size to get the best throughput.  Can any one confirm
this or provide any guidelines?

Thanks in advance.

--
David Fields
Network Specialist
ACS Government Systems
Phone:  (859) 277-8800 x231
david.fields AT acs-inc DOT com

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