Athanasios E. Papathanasiou

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Traditional disk management strategies—prefetching and caching in particular—are designed to maximize performance. In mobile systems they conflict with strategies that attempt to save energy by powering down the disk when it is idle. We present new rules for prefetching and caching that maximize power-down opportunities (without performance loss) by(More)
I/O prefetching serves to hide the latency of slow peripheral devices. Traditional OS-level prefetching strategies have tended to be conservative, fetching only those data that are very likely to be needed according to some simple heuristic, and only just in time for them to arrive before the first access. More aggressive policies, which might speculate(More)
During concurrent I/O workloads, sequential access to one I/O stream can be interrupted by accesses to other streams in the system. Frequent switching between multiple sequential I/O streams may severely affect I/O efficiency due to long disk seek and rotational delays of disk-based storage devices. Aggressive prefetching can improve the granularity of(More)
— Main memory reliability plays a crucial role in overall system reliability. Unfortunately, our collective understanding of the rate, pattern, and impact of memory errors is inadequate and can hinder our ability to innovate new fault-tolerant designs. This paper presents an in-depth study of observed corrected error data from the main memory system of a(More)
The disk array of a server-class system can account for a significant portion of the server's total power budget. Similar observations for mobile (e.g. laptop) systems have led to the development of power management policies that spin down the hard disk when it is idle, but these policies do not transfer well to server-class disks. On the other hand,(More)
Although transactions have been a valuable abstraction of atomicity, persistency, and recoverability, they have not been widely used in programming environments today, mostly because of their high overheads that have been driven by the low performance of magnetic disks. A m a j o r c hallenge in transaction-based systems is to remove the magnetic disk from(More)
World Wide Web traffic increases at impressive rates reaching up to a several million hits (requests/clients) per day for busy Web servers. To serve all these clients effectively, it is necessary to have a good knowledge of their geographic distribution and access patterns. Understanding the geographic distribution of an organization's Web clients is(More)