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spseabra
Contributor
Contributor

Confused about vSphere round-robin iSCSI Multipathing...

Hi all,

Already posted this on NetApp Communities but I hope that any of the gurus on this community can help clarify something for me...

Essentially I would like to know if it's possible to do vSphere iSCSI NMP with only 2 NIC's per FAS node and without stack capable switches (i.e no

cross-switch etherchannel)?

Hypothetical Example:

In this case the core switches don't support any kind of stacking at all, and therein lies the problem.

I know that because of this and if I want a minimum of safety (redundancy) I have to connect each of the 2 NIC's on the FAS node to the 2 Switches.

Example:

Now, I know that in this configuration I only have failover capacity between each NIC on the FAS nodes. But that’s just it, I would like to know if it’s possible using this setup to have multipathing iSCSI using round-robin NMP on vSphere.

Let’s say I configure 2 vmKernel NICS on one ESX vSwitch using IP’s from our example Lan (IP 10.10.0.6 and 10.10.0.7). Bearing in mind that the 2 NICs on the vSphere will be connected in a manner similar to the FAS nodes, one cable to each of the 2 switches.

Now, if I specify round-robin on the 2 vmKernel NIC’s and then use the VIF’s as iSCSI targets, will I get multi-pathing to each node? That is, will the vSphere NMP automatically balance the paths?

Or, do I have to create 1 VIF alias on each node (as suggested by the “vSphere SAN Configuration Guide”) and then use those 4 VIF’s as iSCSI targets?

Confused? You bet Smiley Happy

Thanks in advance

Kind Regards,

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Andy_Banta
Hot Shot
Hot Shot

Let’s say I configure 2 vmKernel NICS on one ESX vSwitch using IP’s from our example Lan (IP 10.10.0.6 and 10.10.0.7).

Bearing in mind that the 2 NICs on the vSphere will be connected in a manner similar to the FAS nodes, one cable to each

of the 2 switches.

If you configure iSCSI Multipathing, as described in the iSCSI SAN Config Guide, chapter 2, you'll be able to use roundrobin. In such a configuration, you'll see 4 paths: 1 from each vmkNIC to each FAS.

If you lower the IOP count for the NMP RoundRobin plugin, you should be ablle to recognize some aggregation, as well.

Enjoy,

Andy

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spseabra
Contributor
Contributor

Hi Andy,

Thanks for the reply.

In the chapter you mentioned, the figure depicts 2 diferente subnets (one for each VMkernel), from what you said I assume this won't be needed for a NetApp system... Because, if that's the case, I won't be able to configure failover in the FAS NIC's with only 2 NIC's per node since I would have to attribute a diferent IP/Subnet combo to each one of the NIC's...

Thanks in advance.

Regards,

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Andy_Banta
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Hot Shot

With some storage, you have to use separate subnets because the storage processors won't allow multiple logins from the same initiator. Other require them in the same subnet because of the way the storage systeme does load balancing. I believe the NetApps can be used either way. For your configuration, put them in the same subnet.

Here's a good overview of the different ways to set up multipathing with vSphere 4:

http://virtualgeek.typepad.com/virtual_geek/2009/09/a-multivendor-post-on-using-iscsi-with-vmware-vs...

Enjoy,

Andy