We present WiscSort, a new approach to high-performance concurrent sorting for existing and future byte-addressable storage (BAS) devices. WiscSort carefully reduces writes, exploits random reads by splitting keys and values during sorting, and performs interference-aware scheduling with thread pool sizing to avoid I/O bandwidth degradation. We introduce the BRAID model which encompasses the unique characteristics of BAS devices. Many state-of-the-art sorting systems do not comply with the BRAID model and deliver sub-optimal performance, whereas WiscSort demonstrates the effectiveness of complying with BRAID. We show that WiscSort is 2-7 x faster than competing approaches on a standard sort benchmark. We evaluate the effectiveness of key-value separation on different key-value sizes and compare our concurrency optimizations with various other concurrency models. Finally, we emulate generic BAS devices and show how our techniques perform well with various combinations of hardware properties.

We present pessimistic locking and optimistic reading (PLOR), a hybrid concurrency control protocol for in-memory transaction systems that delivers high throughput and low tail latency. PLOR is especially designed for high-contention workloads: for high throughput, transactions are allowed to access records without being blocked by lock conflicts in the read phase; for low tail latency, conflict detection is delayed to the commit phase, where old transactions are always committed first using the timestamps in the lock. We demonstrate the efficacy of this approach under a variety of setups (e.g., stored-procedures, interactive mode, and persistent logging, etc.). Experiments show that PLOR delivers close or comparable throughput to that of Silo and TicToc in stored-procedures, while reducing 99.9th percentile latency by 8.8x to 14.5x. In the interactive processing mode, PLOR even achieves up to 2x higher throughput.

New NVM-based devices provide unparalleled performance (i.e., significantly reduced latency) than Flash-based SSDs. In this paper, we look into exploiting an NVM-based block device -- the Intel Optane SSD -- as a caching layer for Microsoft SQL Server. We reveal that naive usage of Optane SSD can result in up to 23% higher query response time than Flash SSD. We explain the issues of simple caching by analyzing the I/O characteristics of Intel Optane SSD. To exploit Optane SSD as a caching layer, we propose an Optane SSD-aware caching strategy including an optimized cache replacement policy and a cache access filter.

Despite the best intentions of disk and RAID manufacturers, on-disk data can still become corrupted. In this paper, we examine the effects of corruption on database management systems. Through injecting faults into the MySQL DBMS, we find that in certain cases, corruption can greatly harm the system, leading to untimely crashes, data loss, or even incorrect results. Overall, of 145 injected faults, 110 lead to serious problems. More detailed observations point us to three deficiencies: MySQL does not have the capability to detect some corruptions due to lack of redundant information, does not isolate corrupted data from valid data, and has inconsistent reactions to similar corruption scenarios. To detect and repair corruption, a DBMS is typically equipped with an offline checker. Unfortunately, the MySQL offline checker is not comprehensive in the checks it performs, misdiagnosing many corruption scenarios and missing others. Sometimes the checker itself crashes; more ominously, its incorrect checking can lead to incorrect repairs. Overall, we find that the checker does not behave correctly in 18 of 145 injected corruptions, and thus can leave the DBMS vulnerable to the problems described above.

We report the performance of NOW-Sort, a collection of sorting implementations on a Network of Workstations (NOW). We find that parallel sorting on a NOW is competitive to sorting on the large-scale SMPs that have traditionally held the performance records. On a 64-node cluster, we sort 6.0 GB in just under one minute, while a 32-node cluster finishes the Datamation benchmark in 2.41 seconds.