We've always put our MTU size at 9000, because we're primarily database-oriented.  However, I have no idea if Linux can support the larger jumbo frames.  9000 definitely works though, and lets 8k database or filesystem blocks fit within one frame, so there's no fragmentation.

Thanks,
Matt

--
Matthew Zito
Chief Scientist
GridApp Systems
P: 646-452-4090
mzito@gridapp.com
http://www.gridapp.com



-----Original Message-----
From: owner-toasters@mathworks.com on behalf of Brent Ellis
Sent: Tue 2/26/2008 9:28 AM
To: toasters@mathworks.com
Subject: Jumbo Packets with netapp FAS3050

Hello All,

We have been using our netapp primarily for NAS storage, but I am 
experimenting with iSCSI now for some specific applications.  I 
managed to create a bit of a network issue recently when I tried 
enabling jumbo packets on my netapp and my test server.  The iSCSI 
connection kept resyncing and was not stable.  I think this was 
because I didn't create a separate vlan for the devices using jumbo 
packets.  Upon further research, I found mention that some devices/
oses calculate the checksums differently and that can affect the max 
packet size.  Does anyone have any recommendations for a packet size 
for both the netapp and for my linux servers?  is 10240 a safe bet(max 
size supported by my switch) or should I use something like 9000 or 
8192?  Should I use a different packet size if I am connecting a 
target to a windows box?  I would ideally like to make a jumbo packets 
vlan and just set all the devices on that vlan to a larger MTU, but I 
don't want to create a network traffic problem in the process.

Brent Ellis
Systems Analyst/Consultant
CAS Computing Services Group
Boston University
interi@bu.edu