Comments on: VMware: What VMkernel Ports means to you http://blog.colovirt.com/2008/12/03/vmware-what-vmkernel-ports-means-to-you/ and linux between Sun, 07 Mar 2010 08:18:39 +0000 http://wordpress.com/ hourly 1 By: Kevin Goodman http://blog.colovirt.com/2008/12/03/vmware-what-vmkernel-ports-means-to-you/#comment-332 Kevin Goodman Thu, 24 Dec 2009 02:04:11 +0000 http://colovirt.wordpress.com/?p=302#comment-332 Even if your kernel port is in a vswitch containing multiple NICS, vmware will only transfer IP based protocols (NFS, ISCSI) through one physical interface. Only time that traffic will go throgh another NIC in that vswitch is if the current ports link fails. Basically there is no True bonding in VMware ESX. Same goes for virtual machines. VMs are assigned to a specific interface in the vswitch when started. Even if there are 4 physical NICs in th vswitch, a VM will ever only use one. The VMWare person is right. By splitting the ports and assignig datadtores to each, it will give you multiple paths to the storage forcing the use of 2 physical ports. In doing so, doubling the speed. Each datastore has to access the San or nas throught a different IP for that to work correctly. This is the reason why a lot of the VMware community have changed to doing software iscsi through the VMs operating system to access storage instead of relying on ESX. Basically creating a base disk in esx to install the OS and then software iscsi or NFS mont more storage through the VMs OS. This spreads the storage traffic through all NICs in the infrastructure. Make sense? Even if your kernel port is in a vswitch containing multiple NICS, vmware will only transfer IP based protocols (NFS, ISCSI) through one physical interface. Only time that traffic will go throgh another NIC in that vswitch is if the current ports link fails. Basically there is no True bonding in VMware ESX. Same goes for virtual machines. VMs are assigned to a specific interface in the vswitch when started. Even if there are 4 physical NICs in th vswitch, a VM will ever only use one.

The VMWare person is right. By splitting the ports and assignig datadtores to each, it will give you multiple paths to the storage forcing the use of 2 physical ports. In doing so, doubling the speed. Each datastore has to access the San or nas throught a different IP for that to work correctly.

This is the reason why a lot of the VMware community have changed to doing software iscsi through the VMs operating system to access storage instead of relying on ESX. Basically creating a base disk in esx to install the OS and then software iscsi or NFS mont more storage through the VMs OS. This spreads the storage traffic through all NICs in the infrastructure. Make sense?

]]> By: Scott Sauer http://blog.colovirt.com/2008/12/03/vmware-what-vmkernel-ports-means-to-you/#comment-331 Scott Sauer Wed, 23 Dec 2009 19:47:22 +0000 http://colovirt.wordpress.com/?p=302#comment-331 I experienced this same issue last week and opened a SR on it. I was also told that the vmkernel port can only use one active nic at a time, which is concerning (I am on vSphere 4u1). We had 4, 1 Gb nics dedicated for the environment. The engineer said to split two and two. Leave two of the nic's in vSwitch0 and then drop another 2 nics into vSwitch1. He also stated that you should have the first vSwitch dedicated to particular data stores, and the second to different or you would see performance degradation. I am looking into if the VMKernel port really does just use one active nic at a time. I am in full agreement, you should be able to pin NFS/iSCSI traffic to particular interfaces much like you can pin VMotion to a particular interface. I experienced this same issue last week and opened a SR on it. I was also told that the vmkernel port can only use one active nic at a time, which is concerning (I am on vSphere 4u1).

We had 4, 1 Gb nics dedicated for the environment. The engineer said to split two and two. Leave two of the nic’s in vSwitch0 and then drop another 2 nics into vSwitch1. He also stated that you should have the first vSwitch dedicated to particular data stores, and the second to different or you would see performance degradation.

I am looking into if the VMKernel port really does just use one active nic at a time. I am in full agreement, you should be able to pin NFS/iSCSI traffic to particular interfaces much like you can pin VMotion to a particular interface.

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