A retaining apparatus for at least one data storage device includes a tray and a retaining device. The tray is used for receiving the at least one data storage device. The retaining device is attached to a front side of the tray. The retaining device includes base member, an arm member, an operation member and a blocking tab. The base member is attached to the front side of the tray. The arm member is pivotably attached to the base member about a first pivot axis. The operation member is pivotably attached to the base member about a second pivot axis. The second pivot axis is substantially perpendicular to the first pivot axis. The blocking tab is secured to the operation member. The blocking tab has a blocking portion to block the arm member.