iSCSI MTU size

[LE2Strat]

OK, I am trying to set up the ISCSI software adapter on a stand alone ESX server wtih 2 paths. Problem is, I am getting the wrong MTU size once added to the iSCSI software adapter.

I created the dedicated Virtual Switch, and set the MTU to 9000

When I do a esxcfg-vswitch -l it shows the switch with MTU of 9000

When I do a esxcfg-nics -l it shows the TWO Nics that are on the switch as MTU 9000.

However, after I add them to the ISCSI software adapter with the commands: esxcli swiscsi nic add -n vmk0 -d vmhba35 for each vmk0 and vmk1, I do a command of: esxcli swiscsi nic list -d vmhba35

It shows the MTU for both vmk0 and vmk1 as 1500.

Why is this so if it's 9000 everywhere else, and how do I change it?

[lamw]

Did you also create the vmkernel interface with MTU set to 9000? There is an option to set the MTU when you create the vmkernel interface

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Twitter: @lamw

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[LE2Strat]

No I did not, I created them from the vCenter GUI.

I saw a post while I was waiting for a resonse here:

http://www.interworks.com/blogs/kculwell/2010/01/29/enabling-jumbo-frames-vmware-esx-4

However, if i add the vmKernel to a Port Group I created, it lets me add the first one, but when I try to add the 2nd one, it tells me there can only be one.

I really don't need a port group.

What is the Syntax from the CLI to add a vmKernel to my vSwith1 and set the correct MTU size without having to use a port group?

[lamw]

You will need to specify a portgroup to bind to, that is a requirement. The syntax is spelled out in the link you referenced.

=========================================================================

William Lam

VMware vExpert 2009,2010

VMware scripts and resources at:

Twitter: @lamw

Getting Started with the vMA (tips/tricks)

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VMware Code Central - Scripts/Sample code for Developers and Administrators

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If you find this information useful, please award points for "correct" or "helpful".

[LE2Strat]

So each NIC I use for iSCSI has to be in it's own Port Group?

OK, I guess I see now, after I create the Port Group and add each IP address I want to use to it, it changes in the vCenter GUI to a VMKernal-Port instead of a VM Network. That was what was confusing me.

[lamw]

Yep, and you will need to specify the MTU on each vmkernel interface as part of the overall requirement for using MTU of 9000 and don't forget to check that your physical switches also supports this and is configured to use jumbo frames

=========================================================================

William Lam

VMware vExpert 2009,2010

VMware scripts and resources at:

Twitter: @lamw

Getting Started with the vMA (tips/tricks)

Getting Started with the vSphere SDK for Perl

VMware Code Central - Scripts/Sample code for Developers and Administrators

VMware Developer Community

If you find this information useful, please award points for "correct" or "helpful".