Across the country, self storage facilities have a mix of security measures. The most secure storage facilities use a combination of automated gates, security cameras, locks on all units, and most importantly, a good location. Storing at a gated facility means that people who are not tenants at the self storage facility cannot enter the premises. The only people afforded access are tenants for whom the facility owner has collected all relevant personal information. There have been times at gated facilities where theft has occurred, but perpetrators are always quick to be caught and face justice, since their personal information is known to the facility management.
Since every tenant is provided with a unique access code, unusual activity can be easily monitored and managed. If for any reason a brake-in occurred, management could immediately alert police as to which gate code was used to gain access. This enables police to quickly catch the criminals and return all stored belongings.
Outside of the aforementioned methods that prevent criminals from gaining access to a facility and help law enforcement catch them, gates serve as a deterrent. If it is so hard to get in, if it's so obvious who entered, why risk it? The odds of being caught and sent to prison are near 100%, and the reward is not worth this. Thus, gated facilities are far more secure than non-gated ones, and one should never store their belongings in an ungated facility.