Container Marking: Combining Data Placement, Garbage Collection and Wear Levelling for Flash

Author(s):  
Xiao-Yu Hu ◽  
Robert Haas ◽  
Eleftheriou Evangelos
1999 ◽  
Vol 34 (3) ◽  
pp. 37-48 ◽  
Author(s):  
Trishul M. Chilimbi ◽  
James R. Larus

2021 ◽  
Vol 11 (24) ◽  
pp. 11842
Author(s):  
Gijun Oh ◽  
Junseok Yang ◽  
Sungyong Ahn

Log-structured merge-tree (LSM-Tree)-based key–value stores are attracting attention for their high I/O (Input/Output) performance due to their sequential write characteristics. However, excessive writes caused by compaction shorten the lifespan of the Solid-state Drive (SSD). Therefore, there are several studies aimed at reducing garbage collection overhead by using Zoned Namespace ZNS; SSD in which the host can determine data placement. However, the existing studies have limitations in terms of performance improvement because the lifetime and hotness of key–value data are not considered. Therefore, in this paper, we propose a technique to minimize the space efficiency and garbage collection overhead of SSDs by arranging them according to the characteristics of key–value data. The proposed method was implemented by modifying ZenFS of RocksDB and, according to the result of the performance evaluation, the space efficiency could be improved by up to 75%.


Life ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 583
Author(s):  
Giulia Furfaro ◽  
Paolo Mariottini

Integrative taxonomy is an evolving field of multidisciplinary studies often utilised to elucidate phylogenetic reconstructions that were poorly understood in the past. The systematics of many taxa have been resolved by combining data from different research approaches, i.e., molecular, ecological, behavioural, morphological and chemical. Regarding molecular analysis, there is currently a search for new genetic markers that could be diagnostic at different taxonomic levels and that can be added to the canonical ones. In marine Heterobranchia, the most widely used mitochondrial markers, COI and 16S, are usually analysed by comparing the primary sequence. The 16S rRNA molecule can be folded into a 2D secondary structure that has been poorly exploited in the past study of heterobranchs, despite 2D molecular analyses being sources of possible diagnostic characters. Comparison of the results from the phylogenetic analyses of a concatenated (the nuclear H3 and the mitochondrial COI and 16S markers) dataset (including 30 species belonging to eight accepted genera) and from the 2D folding structure analyses of the 16S rRNA from the type species of the genera investigated demonstrated the diagnostic power of this RNA molecule to reveal the systematics of four genera belonging to the family Myrrhinidae (Gastropoda, Heterobranchia). The “molecular morphological” approach to the 16S rRNA revealed to be a powerful tool to delimit at both species and genus taxonomic levels and to be a useful way of recovering information that is usually lost in phylogenetic analyses. While the validity of the genera Godiva, Hermissenda and Phyllodesmium are confirmed, a new genus is necessary and introduced for Dondice banyulensis, Nemesis gen. nov. and the monospecific genus Nanuca is here synonymised with Dondice, with Nanuca sebastiani transferred into Dondice as Dondice sebastiani comb. nov.


1977 ◽  
Vol 12 (6) ◽  
pp. 42-48
Author(s):  
Péter Szöke
Keyword(s):  

IEEE Access ◽  
2021 ◽  
pp. 1-1
Author(s):  
M. Maghsoudloo ◽  
A. Rahdari ◽  
N. Khoshavi

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