Umbrella structures exist in most fund jurisdictions: UCITS and AIF umbrellas in Ireland and Luxembourg, SPCs in Cayman and the BVI, series LLCs in the United States. The strength of the separation between sub-funds varies. In an SPC it is statutory; in some other structures it relies on contractual limited-recourse language.
The practical benefit is shared cost and speed. Fixed costs such as directors, audit and regulatory fees are spread across the sub-funds, and a new sub-fund can be added by supplement rather than by forming a new company.