This counter tracks the cumulative number of SCSI blocks written on this LUN within this flow. Paired with ciscoScsiFlowWrIos, an admin can calculate the average write size for this path, distinguishing workloads doing small frequent writes (like transaction logging) from those doing large bulk writes (like backups or bulk data loads). A flow showing a steadily high block-per-IO ratio would be consistent with a nightly backup job's large sequential writes rather than a transactional database's small, frequent commits.