Despite ﬂash memory’s promise, it suffers from many idiosyncrasies such as limited durability, data integrity problems, and asymmetry in operation granularity. As architects, we aim to ﬁnd ways to overcome these idiosyncrasies while exploiting ﬂash memory’s useful characteristics. To be successful, we must understand the trade-offs between the performance, cost (in both power and dollars), and reliability of ﬂash memory. In addition, we must understand how different usage patterns affect these characteristics. Flash manufacturers provide conservative guidelines about these metrics, and this lack of detail makes it difﬁcult to design systems that fully exploit ﬂash memory’s capabilities. We have empirically characterized ﬂash memory technology from ﬁve manufacturers by directly measuring the performance, power, and reliability. We demonstrate that performance varies signiﬁcantly between vendors, devices, and from publicly available datasheets. We also demonstrate and quantify some unexpected device characteristics and show how we can use them to improve responsiveness and energy consumption of solid state disks by 44% and 13%, respectively, as well as increase ﬂash device lifetime by 5.2x.