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Scylla's performance with Samsung Z-SSD

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A comparative study of Scylla performance on Samsung Z-SSD and DRAM New analysis of Samsung’s latency-shattering Z-SSD shows major performance gains when the recently-introduced drive is integrated with the Scylla data store. In this whitepaper, Samsung has closely examined the performance of Scylla — an open-source, high-performance NoSQL data store — on Z-SSD in comparisons with in-memory based architectures. The study also looked at the cost-effectiveness of one solution over the other. With several vertical optimizations in its embedded NAND, SSD controller and SSD memory, Z-SSD reduces read latency more than 5x compared to today’s leading NVMe SSDs. In our tests, we used Scylla, with its finely crafted C++ implementation, as a drop-in replacement for Cassandra. We compared the performance of Scylla when serving requests from memory and when handling them from Samsung’s Z-SSD. To this end, we have characterized system performance as well as overall throughput and latency, using the well-known Cassandra-stress tool. This whitepaper reports our findings, and makes the following observations: • Samsung Z-SSD has shrunk the performance gap between serving data from memory and having the data served from the SSD. • When considering maximum throughput with a constraint of sub-millisecond, 95 percentile latency, and with 50% of requests served from Z-SSD, we have found that the gap between Z-SSD and an in-memory run is only 44% for a read-only workload, and only 40% for a mixed workload (75% read, 25% write). • While Scylla provides a high performance NoSQL service, the overheads of the software stack are considerable – between 6x to 7x compared to the raw device latencies measured with FIO. Further optimizations in the software layer are expected to decrease the gap between SSDs and memory to an even more advantageous level. • Our cost model for performance-per-dollar provides insights into the cost-efficiency of storage systems and highlights the most noteworthy area where Z-SSD could significantly contribute to the building of server systems that are especially cost-efficient. About Scylla ScyllaDB is the world’s fastest NoSQL database. Fully compatible with Apache Cassandra, Scylla embraces a shared-nothing approach that increases throughput and storage capacity to 10X that of Cassandra. AppNexus, Samsung, Mogujie, Outbrain, Kenshoo, Olacabs,, Eniro, IBM’s Compose and many more leading companies have adopted Scylla to realize order-of-magnitude performance improvements and reduce hardware costs. ScyllaDB was founded by the team responsible for the KVM hypervisor and is backed by Bessemer Venture Partners, Innovation Endeavors, Wing Venture Capital, Qualcomm Ventures, Magma Venture Partners, Western Digital Capital and Samsung Ventures. To find out more about the study including methodology and performance results, click the link below to download the whitepaper.