Network design for VMware/iSCSI SAN

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Jan 19th, 2012
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I'm currently in the process of redesigning our corporate network to accommodate the change from standalone servers to a VMware/Equallogic enviroment. We'll be using iSCSI to connect the vm's to the SAN.


My question is as following. How should a proper network design look for this kind of deployment? I've specified my current hardware below that I have to work with. Since I can't set MTU value per port/vlan basis on the 3750/2960 should I dedicate a switch for iSCSI?


Available equipment:


Core switch/router:

WS-C37560G-24TS-1U              


Stacked switches:

WS-C2960S-48TS-L     Access switch              

WS-C2960S-48TS-L     Access switch         

WS-C2960S-48LPS-L   Voice switch         

WS-C2960S-24TS-L     Server switch (Possible dedicated iSCSI switch)        


Non used Stacked switches:

Dell Powerconnect 6224 x 2


Servers:

Dell R710 Quad NIC

Dell R610 Quad NIC


Storage:

Equallogic PS4100 with dual controllers 2 x 1 GbE = 4 GbE for iSCSI



Best regards

Markus

Correct Answer by Jeff Van Houten about 5 years 7 months ago

since the equal logic has dual controllers you're going to want to use a matched pair of switches to cross connect for redundancy. You're going to need some more nics as well. 1 for sc, 1 for vmotion, 2 for iscsi (cross connected) and probably 2 for the production traffic.


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Reza Sharifi Thu, 01/19/2012 - 17:19
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Markus,


You shouldn't need to buy another switch just for ISCSI connectivity.  If you turn on jumbo frame for the entire server switch, that should not effect the equipment that use standards 1500 MTU. Make sure to bundle all the gig interface using an Etherchannel.


HTH

sajid_m123 Mon, 01/23/2012 - 14:22
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Reza,

if jumbo frame is set on one switch in the network and a server connected to it tries to communicate with some machines on different switches with MTU 1500 then won't it cause fragmentations on switches with MTU of 1500?

m.junghage Tue, 01/24/2012 - 04:45
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I think you're correct. I would have to place all clients on a different VLAN and route them in my 3750. The question is if a 2960S stack member can have different MTU then the others.

Correct Answer
Jeff Van Houten Thu, 01/19/2012 - 19:33
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since the equal logic has dual controllers you're going to want to use a matched pair of switches to cross connect for redundancy. You're going to need some more nics as well. 1 for sc, 1 for vmotion, 2 for iscsi (cross connected) and probably 2 for the production traffic.


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m.junghage Tue, 01/24/2012 - 04:41
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I know that double everything would be best for redundancy but this install does not have the budget to purchase another 2960S for these servers and I can't use our shared access switches as the system MTU would differ from our corporate LAN.


What do you mean with "1 for sc"?


I think I'm going to order an extra quad NIC for each server and configure as follows.

2 x Production network

2 x iSCSI

1 x vmotion

1 x iDrac out of band management


On another note. In a switch stack with four 2960S members, is it possible to set Jumbo frames on only one member or do I have to make it a standalone switch?

Jeff Van Houten Tue, 01/24/2012 - 04:49
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sc is service console. VMware recommends a separate physical nic for sc traffic if you are using virtual center for administration.


I'm 99% sure that you cannot set jumbo frames on an individual member of a switch stack but I can't put in a document citation to support that. You'll have to separate the switches.


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