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October 7th, 2009 11:00
How many paths for VSphere 4 to PS100e?
I recently read the Dell Equallogic article TR1049 which gives examples of how to connect your ESX 4.0 to a PS SAN. The example show how to setup 2 physical NICs with three VMKernal ports to each card for iSCSI connectivity. I have a PE2950 connecting to a single PS100e array with v4.1.4 code. I followed the examp,e and setup the VMKernal ports as suggested with three for each physical nic. My confusion comes in here: How do you determine how many VMKernal iSCSI paths are optimal for my situation given I only have one PS100e. I have two controllers which gives me three paths to the SAN eth0, eth1 and eth2. I want to reason that I should only need 3 VMkernals iSCSI paths for multi I/O and not 6 as suggested as I only have three physical ports to load balance traffic on the PS100e. In the example they have two PS arrays which would make sense they would use 6 paths one for each of the three ports on two arrays. Is this logical or is there a formula to figure how many paths need to be setup for optimal perfomance from ESX to PS? Any suggestion will be appreciated. I occasionally have one or more paths drops the connection from the PS100e and I am concerned I have defined too many paths for one device.
Thanks. John Z.
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October 7th, 2009 15:00
Each VMkernel should establish a path to each volume.
If I'm reading your description correctly you have 6 VMkernels set up (2 NICs with 3 VMkernels per NIC). So this should yield 6 iSCSI paths.
Don't forget to change the multipathing setting to "round robin" (from the default "most recently used") on each volume.
johnz333
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October 8th, 2009 07:00
That is correct. I have 6 paths setup, 3 on each NIC and I did change the multi path setup for round robin. My only question was how many paths is optimal. There are really only three paths to the PS100e. I point the 6 VMkernels to the Group IP address of the PS100 and it automatically picks one of the three paths so you when you look at the PS100 connections to that volume you see 6 connections, one from each VMkernel but is this too many? Would it be better to limit the connections to three as the PS100 has only three possible paths or is 6 just as good? I only ask as I saw some of the 6 connections randomly drop for the SAN when I was formatting the 800GB volume for VMFS3. The connections dropped and the event log said that the multi path was degraded but that it was just a warning. Only one of the VMkernels dropped at a time and not the same one every time. It was two from one NIC and the third was from the other NIC. The format finished fine and the dropped connections reattached within seconds. My only concern was maybe I had two many paths and that may have caused the issue? I just wanted to make sure I have the optimal setup before I start migrating physical machines. I guess I could build a few "test" VM's and see what happens with my 6 connections during a test load.