Spencer W. Ng

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Large archival storage systems experience long periods of idleness broken up by rare data accesses. In such systems, disks may remain powered off for long periods of time. These systems can lose data for a variety of reasons, including failures at both the device level and the block level. To deal with these failures, we must detect them early enough to be(More)
RAID5 tolerates single disk failures by exclusive-ORing (XORing) the blocks corresponding to a requested block on the failed disk to reconstruct it. This results in increased loads on surviving disks and degraded disk response times with respect to normal mode operation. Provided a spare disk is available, a rebuild process systematically reads successive(More)
RAID5 performance is critical while rebuild is in progress, since in addition to the increased load to recreate lost data on demand, there is interference caused by rebuild requests. We report on simulation results, which show that processing user requests at a higher, rather than the same priority as rebuild requests, results in a lower response time for(More)
There is a continuing need to improve the performance of disk subsystems, and one of the key factors of a disk subsystem's performance is the data transfer rate. While it is clear that increasing the data transfer rate would reduce the service time for those applications that move large amounts of data per I/O, the amount of data transferred per I/O in many(More)