Recently I went to extend a volume on one of my guest systems and received an error requiring me to power off the system before extending the disk.

ErrorHot-extend was invoked with size (5368709120 sectors) >= 2TB. Hot-extend beyond or equal to 2TB is not supported. The disk extend operation failed: msg.disklib.INVAL

Good News – With vSphere 6.5 this is no longer a limitation.

Just one more reason why you should think about upgrading your VMware environment to the latest.