There are few use cases for it. One is for all these people who benchmark stuff and want selective OS cache purges, another is for those who run high performance databases. Remember the O_DIRECT serialization everywhere? Well, XFS does direct I/O in parallel, unless there are cached pages (and they can happen because of any random outside-of-database activity, like ‘file’ command). Once you ‘uncache’ the files, XFS will be very much parallel again \o/ \o/
Site Reliability Engineering (SRE) at Facebook is always under pressure to keep the site and all the moving pieces behind the scenes running while still delivering an excellent user experience. The recent launch of usernames to our 200 million active users on a single night at the exact same time was unique in its preparation and potential for trouble. Our product teams had evaluated the various options for enabling people to register for their name and decided upon a single first come, first serve registration window for every user. Although this was the most fair, it was difficult operationally because predicting the number of users that would show up at that time to claim a name was impossible.
Abstract: High-scale cloud services provide economies of scale of five to ten over small-scale deployments, and are becoming a large part of both enterprise information processing and consumer services. Even very large enterprise IT deployments have quite different cost drivers and optimizations points from internet-scale services. The former are people-dominated from a cost perspective whereas internet-scale service costs are driven by server hardware and infrastructure with people costs fading into the noise at less than 10%.
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