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BrandonB
Asked: 2011-06-16 07:32:28 +0800 CST

To LAG or not LAG?

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I have a new ex4200 switch stack, my 3 esxi hyper-visors connect to the SAN via vlan 200 which is EST. I have loaded the Equallogic multipathing plugins. When I have the 4 cables per server dedicated plugged in to the switch the hyper-visor see's 4 paths like it should. When I lag 2 ports and 2 ports together I only get two paths. This is expected behavior however what is better ? Use 2 2g links dictated by the switch or use 4 paths and let the plugin do it's job ?

networking storage-area-network iscsi vmware-esxi juniper

3 Answers

  1. Best Answer

    With your SAN, let MPIO do its job and do not use LAGs with the server or SAN connections. You can (and should) use LAGs or LACP trunks between the switches though.

    Here is the EqualLogic configuration guide with more information on this topic [Section 4.5]: http://en.community.dell.com/dell-groups/dtcmedia/m/mediagallery/19852516/download.aspx

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  2. I would always use as many LACP trunk members as practical, not only for resilience but for potential performance benefits too, so I'd let the plugin do its job.

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  3. I am assuming that you are connecting your storage via iSCSI. If so, definitely let the MPIO do its thing, instead of aggregation. However, if you decide to use NFS, you have to keep in mind that with one datastore there will only be one TCP session and loss of that session means a loss of your datastore, so you are going to need something to give you added layer of redundancy. Datastore diversity is important with NFS, as this way you can distribute and reduce impact of failure. In cases where NFS is used LAG id a good option. Critically, far too often people forget that their single switch is a SPOF, and they do nothing about it. I am personally a firm believer in cross-stack aggregation, which eliminates the switch as a SPOF.

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