A non-volatile storage subsystem maintains, and makes available to a host system, monitor data reflective of a likelihood of a data error occurring. The monitor data may, for example, include usage statistics and/or sensor data. The storage subsystem transfers the monitor data to the host system over a signal interface that is separate from the signal interface used for standard storage operations. This interface may be implemented using otherwise unused pins/signal lines of a standard connector, such as a CompactFlash or SATA connector. Special hardware may be provided in the storage subsystem and host system for transferring the monitor data over these signal lines, so that the transfers occur with little or no need for host-software intervention. The disclosed design reduces or eliminates the need for host software that uses non-standard or “vendor-specific” commands to retrieve the monitor data.