Configuring Multipath iSCSI for ESX? Here’s the Setting You Forgot.

I finished a story today for this website titled Configuring Highly-Available iSCSI Storage for ESX 4.0.  That story, which will be released in the upcoming days, outlines the exact steps you’ll use to create a multipath iSCSI connection between servers and storage. Yet, while writing it I couldn’t avoid the nagging feeling that one step in that configuration may get forgotten in some environments.  Most of us know that iSCSI doesn’t like teamed network connections, preferring to use its own multipathing technology.  Most of us correctly configure our NICs so that there is a 1:1 mapping between NICs and VMkernel ports.  Most of us probably also know to check the box to Override vSwitch failover order, and then to configure the Active Adapters for that 1:1 mapping. (If you didn’t know these steps, drop back on by in a couple of days.  I’ll re-post this with a link to the entire step-by-step story once published). But some of us might not know that a final step in the process requires mapping VMkernel ports to the iSCSI Software Adapter itself.  Turns out doing this, at least in ESX 4.0 Update 1, requires work from the command line.  That command is: esxcli swiscsi nic add –n -d In the syntax above, you’ll need to replace with the correct VMkernel ports you associated with the vSwitch.  is typically replaced with vmhba33 or whatever is your correct identifier for the iSCSI Software Adapter. To verify that you’ve got the proper mapping, bring up the vSphere CLI on all your servers and run the command: esxcli swiscsi nic list –d vmhba33 If you get the right list of adapters back, you’re good to go.  If not, you might double-check your configuration.   All the virtualization tips and tricks you can handle at:  http://www.windowsitpro.com/categories/category/Virtualization/GregShieldsonVirtualization.aspx!