From where the Virtual Firedrill pick the disk for creating the snapshot

Enviroment

SFHA/DR = 6x

OS = rhel 6x

Query

I have read the guide VCS admin guide 6.0 for linux, Page 567, topic "Running the FireDrill Setup". I am unable to see where we keep the disk with free space(seems that disk should be in the same DiskGroup in which replicated Volume exist of DR site), so that a duplicated copy will be made of Replicated volume/mount point at secondary/DR site which will be use in Virtuall FireDrill.

Need some words on work which should be done before running the Firedrill setup