Sectors Written (low). The phyDrvHWrites and the phyDrvWrites together shows the total number of sectors written to the physical disk drive during the reference hours (phyDrvRefHours). The actual number of sectors written equals the phyDrvHWrites times 2^32 plus the phyDrvWrites. This information may be useful for determining rates. For instance, if you wanted to calculate the average number of writes per hour of operation, divide this number by the reference hours.