Re: [Moosefs-users] MooseFS and Generic Segmentation Offload in CentOS

[Michał B. <mic...@ge...>]

Hi Ólafur!

Thank you for your tip! We added this information in our FAQ entry:
http://www.moosefs.org/moosefs-faq.html#mtu


Kind regards
Michał Borychowski 
MooseFS Support Manager
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Gemius S.A.
ul. Wołoska 7, 02-672 Warszawa
Budynek MARS, klatka D
Tel.: +4822 874-41-00
Fax : +4822 874-41-01



-----Original Message-----
From: Ólafur Ósvaldsson [mailto:osv...@ne...] 
Sent: Wednesday, December 01, 2010 11:41 AM
To: moo...@li...
Subject: [Moosefs-users] MooseFS and Generic Segmentation Offload in CentOS

Hi,
I just wanted to give a heads up if anyone gets into the same problems as we
did here.

Our new setup is like this:

1 x Master (Ubuntu 10.04)
1 x Metalogger (Ubuntu 10.04)
10 x Chunkservers (Ubuntu 10.04)

And then we have for testing 8 CentOS 5.5 servers using the MFS.

All Ubuntu servers have Broadcom BCM5708 network cards and the CentOS blades
have BCM5709 and this is all connected through Cisco 3560 and 2960 switches.

Everything was working fine after the initial install and then I set
Jumbo-Frames on the switches and changed the MTU on all the servers to 9000,
and by that point I could only get a listing of files but we were unable to
read the contents of large files on MFS mounts from the CentOS machines, but
if the filesystem was mounted from the Master it worked fine.

Direct communication seemed to work fine, ping with different size packets,
ssh and other services did not fail.

After a couple of days looking at this I found that the operating systems
have different driver settings for atleast Broadcom cards, while Ubuntu has
a switch called "generic segmentation offload" set by default to on, CentOS
has the switch set to off, by changing this setting on the CentOS machines
it now runs fine just like before.

To set it you use "ethtool -K gso on"

/Oli

--
Ólafur Osvaldsson
System Administrator
Nethonnun ehf.
e-mail: osv...@ne...
phone: +354 517 3418


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