Dell POWERVAULT MD3200I Configuration Manual page 57

Dell PowerVault MD3200i/MD3600i Configuration Guide for VMware ESX4.1 Server Software
failover alternate path. This LUN/controller relationship is reported by the MD3200i/MD3600i
to VMware which then dictates the paths (and the "optimal" condition of the array).
On the MD3200i/MD3600i, setup each port on a different subnet with one disk group per
controller, each disk group with 4 LUNS (one LUN per port).
Regardless of the pathing method in VMware, without separate subnets a bottle-neck at the
controller <will arise> since pathing is at the disk group level rather than the LUN level for the
MD3200i/MD3600i.
Configuring RR to the same LUN across both controllers is not recommended.
Here are the ESXi CLI commands to switch the pathing policy. You run this for each device. Note,
this can also be accomplished via the GUI.
esxcli nmp device setpolicy --device < device name > --psp VMW_PSP_MRU
esxcli nmp device setpolicy --device < device name > --psp VMW_PSP_RR
esxcli nmp device list
The number of servers, and physical NICs as well as the I/O access characteristics will affect how
you configure the MD3200i/MD3600i. Performance depends on many variables. For example, if
you have lots of random data going to one LUN and lots of sequential data on another LUN, you
might want them to be on separate disk groups as all that random movement could inhibit
performance of the sequential data. Now, if all the data is sequential, you might get better
performance keeping both the LUNs on a large disk group and take advantage of spindles. So, a
lot depends on the nature of your data.
A performance tuning guide that talks about various variables that you can play with and how
each might impact performance is available here.
Using the MD Configuration Utility(MDCU)
This utility provides a wizard for configuring ports on an MD300xi. A user would employ this on
a guest OS under an established VM.
Considerations involving Volume Not On Preferred Path
Virtual Disk Not On Preferred Path(VNOP) condition is the result of a Virtual Disk (a.k.a. LUN)
being assigned to the alternate controller from its original assignment when first created.
This situation can arise as a combination of default settings for Virtual Disk creation in the
MD3200i and the creation of active iSCSI sessions between the host and the MD3200i for iSCSI
June 4, 2012 Page 57