The maturity of the telecommunications market and the fact that user demands increase every day leaves network operators no option but to deploy high-speed infrastructures and test them in an efficient and economical manner. A common approach to this problem has been the storage of network traffic samples for analysis and replay using different versions of what we have named NTSS. This type of task is particularly demanding in 10 Gb Ethernet links and has traditionally been addressed by closed solutions or NTSS built on top of high-end hardware. However, these approaches lack flexibility and extensibility, which typically translates into higher cost. This work studies how NTSS can be built using COTS: a combination of commodity hardware and open source software. To this end, we present the current limitations of COTS systems and focus on low-level optimization techniques at several levels: the NIC driver, hard drives, and the software interaction between them. The application of these techniques has proven crucial for reaching 10 Gb/s rates, as different state-of-the-art systems have shown after an extensive performance test.