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timn1
1 Copper

Adding an MD3200i to an existing EQL environment (VMware)

Hi,

I've just racked up and configured an MD3200i with the intention of using it for 'Tier2' storage to take capacity pressure off the SAN.  

My question specifically relates to the best way to handle the 'best practice' subnetting model for the MD3200i array and the VMware 'don'ts' when it comes to multiple subnets for vmhba's.

Here's a rough idea of what I have now:

  • Multiple hosts with 4 dedicated NICs each on dedicated switches all set up using best practice for iSCSI EQL SAN deployment (two stacks/LAG for redundancy).
  • All SAN iSCSI traffic is on one subnet (ie all host vmhba's and SAN eth ports are talking on one subnet) and the backend (Dell N3048) switches happily pass the subnet across the LAG between them.
  • I have 4 NICs on each host all bound on a 1:1 basis to an iSCSI vmkernel (total 4 IPs per host, all on same subnet)
  • The MD3200i is currently sitting at factory default IP addressing on the controllers with four subnets and 8 IPs all up (2 per subnet, each subnet vertically aligned - C0-0 & C1-0, C0-1 & C1-1 etc)

According to VMware (see this KB article) mixing different broadcast domains/subnets on vmhba's can excessively extend re-scan times.  VMware stipulate we should put ALL our iSCSI traffic on a single domain as the traffic is not routable. 

So, I could theoretically put all my MD3200i eth ports on the same subnet as my EQL eth ports/host initiators to satisfy the ESXi requirements (backend switching will support either/or by the way).  However, my first concern is what impact might this have if I inadvertently load up my vmhba (software) iSCSI adapters with 8 NICs with 1:1 bindings to 8 real NICs

Second concern is what the likely impact to performance on the MD3200i will be given all traffic is now on one subnet and Round Robin (VMware) is no longer an option.  Is my only choice therefore to used Fixed Path for the devices?

In conclusion, I'm looking for any real world (or awesome theories!) information on mixing iSCSI targets on one subnet with EQL/MD3200i/VMware ESXi/Windows iSCSI all in the mix.

By the way, it's not an option for me to add NICs to the hosts nor add more switches.  I really need to make what I have work.  I will, however, accept using as little as two ports (one per controller) on the MD3200i if it's absolutely the only way to make it work.

Thanks.

Infrastructure Engineer, Network novice, unashamed Dell/EQL fanboy and Crash Test Dummy.

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