The Unwritten Contract of Solid State Drives
We perform a detailed vertical analysis of application performance atop a range of modern file systems and SSD FTLs. We formalize the “unwritten contract” that clients of SSDs should follow to obtain high performance, and conduct our analysis to uncover application and file system designs that violate the contract. Our analysis, which utilizes a highly detailed SSD simulation underneath traces taken from real workloads and file systems, provides insight into how to better construct applications, file systems, and FTLs to realize robust and sustainable performance.
(via Nelson)(tags: via:nelson optimization performance ssd disks storage coding architecture)
COVID-19 correlate of protection identified
Via Keith Dawson:
A large study out of Australia has added to the accumulating evidence that the level of neutralizing antibodies circulating in the blood is highly correlated with protection against symptomatic Covid-19. Ars Technica has a good summary of the research and what it means. It’s known that antibody levels decline with time. This work also gave hints about how long protection against disease might last after natural infection or vaccination — which bears on whether or when we might need a booster shot. The Ars reporter writes: ‘A vaccine with 95% efficacy after the second dose would still have an estimated 77% efficacy 250 days out. And that’s for protection against a symptomatic infection. The protection against severe COVID-19 is much stronger and would likely take far longer to decline… A starting efficacy of 70% would be down to 33% efficacy at 250 days.’ The model the researchers developed was able to predict, with good accuracy, the efficacy a vaccine should show in Phase III trials based on the antibody levels measured in Phase I and II.
(tags: vaccination virology vaccines covid-19 sars-cov-2 via:kdawson antibodies)