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Box293
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Question about iSCSI Initiators and multiple NIC's

I've been reading the attached document.

The document talks about creating multiple iSCSI initiators to talk to the SAN (I understand this bit).

Page 15 Step 4: Associate VMkernel Ports to Physical Adapters

The document talks about 3 NICs that have been assigned to a vSwitch.

The document then go on talking about creating individual path bindings for each VMkernel to a NIC.

My question is:

Why do this?

Why not create three seperate vSwitches and create an iSCSI initiator for each vSwitch?

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Andy_Banta
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Why wouldn't you create a vSwitch for each NIC and VMkernel iSCSI port. Why does the document insist on puttting all the NIC's in one vSwitch?

The number and type of vSwitches isn't interesting. You can use one vSwitch or as many vSwitches as you have physical NICs. This works for both legacy static vSwitches or vDS, as well. The configuration example is just one of the ways you can do it. Any combination is supported.

Andy

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Narkis
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My question is:

Why do this?

For MPIO ( Multi path to a iSCSI Volume ) and better performance, fine tuning as per the documents.

Why not create three seperate vSwitches and create an iSCSI initiator for each vSwitch?

Cannot create multiple SOFTWARE iSCSI initiators on a host. This document talks about software iSCSI initiator. 3 vSwitches are not required when we achive on a single vSwitch , in that example they explain to implement Mpath on a Single vswitch. ( Page 16 will give u better understanding ) .Cheers!

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Box293
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So it's all about the MPIO and it cannot work if each iSCSI initiator is in a different vSwitch?

When I read through the document it creates three iSCSI initiators and then binds them to each NIC. Because three NICs are part of the same switch it then goes through remove the bindings for the other two nics.

I would have thought that if you wanted each NIC to be bound to each iSCSI initiator then it would be super simple to create 3 vSwitches and assign 1 nic per vSwitch and create 1 iSCSI initiator per vSwitch.

I'm not saying it should work that way, there just seems a lot of tweaking and configuration to make this work.

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Narkis
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Buddy,

Do you mean Software iSCSI initiator ? or Hardware iSCSI initiatior. you mentioned 3 iscsi initiotrs then it should be hardware iSCSI. Correct me if I am wrong we can not create more than one software iSCSI intiator per host. Cheers!

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Stu_McHugh
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I use a DL380 and of that use 2 NIC for my iSCSI traffic on it's own vSwitch. Once that is setup I follow NetApp's best practice and use a round robin configuration which utilizes both NIC's. It could be worth checking your SAN documentation to see what it advises as best practice for VMware.

Stuart

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Box293
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Software Initiators.

I think I am getting the terminology wrong. I think I need to be saying VMkernel iSCSI port.

Page 10 explains:

In a default configuration assign one VMkernel port for each physical NIC in the system. So if there are 3 NICs, assign 3 VMkernel Ports. This is referred to in the VMware iSCSI document as 1:1 port binding.

And then the document goes on about how to do this (by creating 1 vSwitch).

Why wouldn't you create a vSwitch for each NIC and VMkernel iSCSI port. Why does the document insist on puttting all the NIC's in one vSwitch?

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FranckRookie
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Hi Guys,

On an ESX server, you have only one iSCSI software initiator. Then you attach several vmkernel ports to have different paths to your storage.

Having one vSwitch should be a question of simplicity. Why do you want to create several vSwitches when a single one is enough? When binding vmkernels to the iSCSI initiator, it does not care about which vSwitch the vmkernel is attached to. So it should work either ways (please, correct me if I'm wrong!).

Second think is that, if your system grows and you want to change your configuration from (1:1) to (x:1), it won't be possible if you have your physical nics spread over several vSwitches. With a single one, it gives you this flexibility.

Regards

Franck

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Andy_Banta
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Why wouldn't you create a vSwitch for each NIC and VMkernel iSCSI port. Why does the document insist on puttting all the NIC's in one vSwitch?

The number and type of vSwitches isn't interesting. You can use one vSwitch or as many vSwitches as you have physical NICs. This works for both legacy static vSwitches or vDS, as well. The configuration example is just one of the ways you can do it. Any combination is supported.

Andy

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Box293
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Great Andy, this was the information I was after.

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Box293
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Hey Franck,

When reading the attached document it went through some extra steps that seemed like additional work (removing the iSCSI VMkernel bindings from the unused nics in the team).

I was trying to find out if this is the same as having three seperate switches, as this would mean less addititional manual configuration.

Andy has answered my question.

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FranckRookie
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Andy,

Not sure you will need fewer commands to configure one vSwitch per vmkernel. You have to create several vSwitches and configure jumbo frames on all of them. But yes, you can have one vSwitch per vmkernel.

Doing this, you will lose all flexibility. And how much time will you save: a few seconds?

Following Dell's document, having all cards and vmkernel ports on the same vSwitch allows modifying your configuration easily if necessary. You can find such presentations from other vendors.

Regards

Franck

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Andy_Banta
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Franck,

All I'm pointing out is that it works regardless of your vSwitch configuration. How you configure vSwitches should be done based on other system factors. iSCSI Multipathing works with whatever that configuration is.

Andy

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Box293
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Andy,

It's not about saving time but trying to understand what is a simple configuration (in my mind).

If I follow the example in the document, there more additional manual steps. While this is not a problem, further down the track it may cause issues. If someone removed a NIC from a team and added it again, they would need to go and perform these manual steps again (that's if they go and look at the documentation we created).

If each NIC was in it's own switch then there is no need to do additional commands to setup 1:1 bindings.

I also do understand your point about flexibility.

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Box293
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Just as an FYI, when I was installing the EqualLogic Multipathing Module, the setup.pl command has a wizard to do the switch setup / configuration for you.

The --configure operation can be run in an interactive mode by specifying only the server name parameter. The script then interactively asks the user a series of questions to gather the necessary information for network configuration.

This makes things much easier, let the script do it for you.

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