Distributed storage systems support failures of individual devices by the use of replication or erasure correcting codes. While erasure correcting codes offer a better storage efficiency than replication for similar fault tolerance, they incur higher CPU consumption, higher network consumption and higher disk I/Os. To address these issues, codes specific to storage systems have been designed. Their main feature is the ability to repair a single lost disk efficiently. In this paper, we focus on one such class of codes that minimize network consumption during repair, namely regenerating codes. We implement the original Product-Matrix Regenerating codes as well as a new optimization we propose and show that the resulting optimized codes allow achieving 790 MB/s for encoding in typical settings. Reported speeds are significantly higher than previous studies, highlighting that regenerating codes can be used with little CPU penalty.