Many VMware ESX administrators are quite comfortable with fibre channel storage but have not ventured into the iSCSI world. I recently set up my first iSCSI configuration for a small VMware Infrastructure 3 installation and it was quite successful. Here are some takeaways:
iSCSI is quite easy to configure. ESX’s iSCSI support is fully available in the form of a software initiator that uses a VMkernel interface. “That easy?” you ask? Yes, it is really that easy.
Using Ethernet is convenient. Until this point, I have exclusively used fibre channel storage for virtual machine file system (VMFS) volumes. With the ESX iSCSI software initiator, I simply dedicated some gigabit network interface cards to the VMkernel interface and was ready to configure the iSCSI adapter. There is experimental support for a hardware initiator with the QLogic 4010 interface.
There is a minimal configuration for the storage adapter. ESX has an iSCSI software adapter listed in the storage adapters section of the VMware Infrastructure Client. Once you configure this interface, the system is ready to receive a LUN. The figure below shows the configuration of the software iSCSI interface:
After those pointers, I was quickly running with a LUN provided from the storage system. Once the LUN is presented to the host, it is indistinguishable from other VMFS volumes. Full VMotion, Distributed Resource Scheduler and other VMware tools are available on these volumes, including the esxcfg- series of commands.
If you are getting started with iSCSI, be sure to go through the drills related to configuration steps on ESX. Also, visit your system architecture plan and make sure that the iSCSI interfaces are provisioned well by not also holding other traffic, and be sure to check out VMware’s iSCSI configuration document available for download from the VMware website.