I would recommend, leave it to default NMP policy as "Fixed".

If you have multiple LUNs, make sure "preferred path" from NMP is properly balanced across FA's.

i want to clear one thing,will Vmware ESXi 4.1.0 supports round robin policy for Active/Active Storage.

Round robin should be better if the array is an active/active setup. I have never used DMX-3 but VMAX, they should be similar.

It should, refer to http://www.vmware.com/pdf/vsphere4/r40/vsp_40_esx_server_config.pdf

Since I do not have such a setup, it is highly recommend you perform some read/write test before you make the final decision.

For example, you can use "time dd if=... of=..." to have a basic benchmark to see the performance change with the same LUN.

Round Robin is fully supported at that ESX level for Symmetrix arrays and is the recommended PSP to use. It has been certified by VMware and EMC to do so. In ESXi 5.1 and later it is the default PSP for Symmetrix devices (DMX or VMAX)

I would highly recommend the following:

1) Review the "Using EMC Symmetrix Storage in VMware vSphere Environment" TechBook

https://support.emc.com/docu33910_TechBook:-Using-EMC-Symmetrix-Storage-in-VMware-vSphere-Environments.pdf

While it is certainly a good all around read (in addition to the VMware Host Connectivity Guide), in regards to your specific inquiry, you can skip to the following section:

Path Management (p.77)

2) Install at a minimum the Path Management VSI plug-in (of course you may also want to consider the Storage Viewer and Storage Pool plug-ins).

The VSI plug-in(s) make a cameo appearance (yes, they are stars/gems) and are summarized in the few short pages in the TechBook above

Latest are v5.5 (available under Resources: Downloads)

https://support.emc.com/search/?resource=DOWN&AlloftheseWrds=VSI&SearchWithin=true&adv=y

Since "Fixed" is the default PSP (path selection policy) for v4.1, instead of for every individual LUN and repeating on every ESX server one at a time changing from "Fixed" to "Round-Robin", with the Path Management VSI plug-in, you can for instance, right-click on a Cluster in the vSphere Client inventory and change in bulk by selecting, for instance, "All Symmetrix Devices" use "Round-Robin".

3) In regards to Round-Robin, instead of the default 1000 IOPs for the "I/O Operation Limit", we recommend changing to 1

As mentioned in the document:

[...]

Tuning the Round Robin I/O operation limit parameter can significantly improve the performance of certain workloads, markedly so in sequential workloads.  In case of environments which have random and OLTP type 2 workloads in their environments setting the Round Robin parameter to lower numbers still yields the best throughput; however lowering the value does not improve performance as significantly as it does for sequential workloads.

For these reasons, EMC recommends that the NMP Round Robin I/O operation limit parameter be set to 1.  This ensures the best possible performance regardless of the workload being generated from the vSphere environment.

[...]

On top of what Chris said you can run:

esxcli storage nmp satp rule add -s "VMW_SATP_SYMM" -V "EMC" -M "SYMMETRIX" -P "VMW_PSP_RR" -O "iops=1"

This will cause all new devices added to the ESXi host that use RR to automatically get the IOPS=1 configuration instead of 1000.

Hi Chris

Thanks for your reply, i got that we can enable "Roundrobin" policy for Active/Active Storage arrays.And has some queries regarding this.

1) Have to make any changes to claim rules defined in /var/vmware/esx.conf file before changing NMP policy?

2)And am unable to find how to change from "Roundrobin" to "Fixed" policy without any impact as datastore's created on ESX server are been utilizing by Virtual servers.?

3)

3) In regards to Round-Robin, instead of the default 1000 IOPs for the "I/O Operation Limit", we recommend changing to 1

     Can we change "I/O operation Limit" to 1 through Vsphere client.?

Pls let me know there are any other concerns we have to take care while changing NMP policy.

Thanks in Advance.

1: You shouldn't have to mess with claim rules

2. You can change between PSPs for a given device with zero disruption in service. This can be done in the vSphere Client

3. No, this parameter can only be changed via CMD line.