  In recent years, high availability and reliability of Data Storage Systems
(DSS) have been significantly threatened by soft errors occurring in storage
controllers. Due to their specific functionality and hardware-software stack,
error propagation and manifestation in DSS is quite different from
general-purpose computing architectures. To our knowledge, no previous study
has examined the system-level effects of soft errors on the availability and
reliability of data storage systems. In this paper, we first analyze the
effects of soft errors occurring in the server processors of storage
controllers on the entire storage system dependability. To this end, we
implemented the major functions of a typical data storage system controller,
running on a full stack of storage system operating system, and developed a
framework to perform fault injection experiments using a full system simulator.
We then propose a new metric, Storage System Vulnerability Factor (SSVF), to
accurately capture the impact of soft errors in storage systems. By conducting
extensive experiments, it is revealed that depending on the controller
configuration, up to 40% of cache memory contains end-user data where any
unrecoverable soft errors in this part will result in Data Loss (DL) in an
irreversible manner. However, soft errors in the rest of cache memory filled by
Operating System (OS) and storage applications will result in Data
Unavailability (DU) at the storage system level. Our analysis also shows that
Detectable Unrecoverable Errors (DUEs) on the cache data field are the major
cause of DU in storage systems, while Silent Data Corruptions (SDCs) in the
cache tag and data field are mainly the cause of DL in storage systems.
