Measuring and Improving Memory’s Resistance to Operating System Crashes
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چکیده
Memory is commonly viewed as an unreliable place to store permanent data because it is perceived to be vulnerable to system crashes.1 Yet despite all the negative implications of memory’s unreliability, no data exists that quantifies how vulnerable memory actually is to system crashes. The goals of this paper are to quantify the vulnerability of memory to operating system crashes and to propose a method for protecting memory from these crashes. We use software fault injection to induce a wide variety of operating system crashes in DEC Alpha workstations running Digital Unix, ranging from bit errors in the kernel stack to deleting branch instructions to C-level allocation management errors. We show that memory is remarkably resistant to operating system crashes. Out of the 996 crashes we observed, only 17 corrupted file cache data. Excluding direct corruption from copy overruns, only 2 out of 820 corrupted file cache data. This data contradicts the common assumption that operating system crashes often corrupt files in memory. For users who need even greater protection against operating system crashes, we propose a simple, low-overhead software scheme that controls access to file cache buffers using virtual memory protection and code patching.
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تاریخ انتشار 2000