Reducing SSD Read Latency via NAND Flash Program and Erase Suspension

Abstract In NAND flash memory, once a page program or block erase (P/E) command is issued to a NAND flash chip, the subsequent read requests have to wait until the timeconsuming P/E operation to complete. Preliminary results show that the lengthy P/E operations may increase the read latency by 2x on average. As NAND flashbased SSDs enter the enterprise server storage, this increased read latency caused by the contention may significantly degrade the overall system performance. Inspired by the internal mechanism of NAND flash P/E algorithms, we propose in this paper a low-overhead P/E suspension scheme, which suspends the on-going P/E to service pending reads and resumes the suspended P/E afterwards. In our experiments, we simulate a realistic SSD model that adopts multi-chip/channel and evaluate both SLC and MLC NAND flash as storage materials of diverse performance. Our experimental results show that the proposed technique achieves a near-optimal performance gain on servicing read requests. Specifically, the read latency is reduced on average by 50.5% compared to RPS and 75.4% compared to FIFO at cost of less than 4% overhead on write requests

Correlations between negative life events and suicidal ideation among Chinese adolescents: a meta-analysis

BackgroundSuicide ideation (SI) has become a serious social issue worldwide, and research has found a certain correlation between negative life events (NLE) and SI. Nevertheless, this relationship is still not clear among Chinese adolescents, a special population. Hence, this investigation performed a meta-analysis of observational research on the correlation between NLE and SI among adolescents in China, to further clarify the association.MethodsWe performed an extensive search on seven electronic databases starting from their establishment until March 10, 2023. The research mainly focused on cross-sectional studies conducted on samples of Chinese adolescents. To examine the association between NLE and SI, a meta-analysis model using random effects was utilized. To investigate moderating factors such as age, region, assessment tools for SI, and year of publication, subgroup and meta-regression analyses were performed. The AHRQ evaluated the quality of the study. The synthesis of data was conducted utilizing STATA software (version 16).ResultsUltimately, a total of 30 cross-sectional studies were selected for this analysis, including 39,602 individuals in the participant sample. The results showed that NLE was moderately positively correlated with SI among Chinese adolescents (r = 0.29, 95% CI: 0.26, 0.32). In addition, this relationship was moderated by regional differences and the measurement tool used for SI. Studies conducted in Western China showed a higher correlation coefficient than those conducted in Eastern and Central China. Moreover, research conducted with the SSIOSS demonstrated a stronger correlation coefficient compared to studies utilizing the BSI-CV or other assessment instruments.ConclusionThis meta-analysis indicates that NLE is linked to SI in Chinese teenagers, especially those residing in Western regions of China. Identifying and intervening in NLE and associated risk factors are crucial to prevent suicide within this demographic

A caching strategy to improve iscsi performance

iSCSI is one of the most recent standards that allows SCSI protocols to be carried out over IP networks. However, to encapsulate SCSI protocol over IP requires significant amount of overhead traffic for SCSI commands transfers and handshaking over the Internet. In this paper, we propose a caching scheme, called iCache, to improve the iSCSI performance. iCache uses a log disk along with a piece of non-volatile RAM to cache the iSCSI traffic. Through efficient caching algorithm, iCache can significantly improve performance over current iSCSI systems. Numerical results using popular benchmark program and real world trace have shown dramatic performance gain.