PinK: High-speed In-storage Key-value Store with Bounded Tails

Key-value store based on a log-structured merge-tree (LSM-tree) is preferable to hash-based KV store because an LSM-tree can support a wider variety of operations and show better performance, especially for writes. However, LSM-tree is difficult to implement in the resource constrained environment of a key-value SSD (KV-SSD) and consequently, KV-SSDs typically use hash-based schemes. We present PinK, a design and implementation of an LSM-tree-based KV-SSD, which compared to a hash-based KV-SSD, reduces 99th percentile tail latency by 73%, improves average read latency by 42% and shows 37% higher throughput. The key idea in improving the performance of an LSM-tree in a resource constrained environment is to avoid the use of Bloom filters and instead, use a small amount of DRAM to keep/pin the top levels of the LSM-tree. Copyright © Proc. of the 2020 USENIX Annual Technical Conference, ATC 2020. All rights reserved

Design of LSM-tree-based Key-value SSDs with Bounded Tails

Key-value store based on a log-structured merge-tree (LSM-tree) is preferable to hash-based key-value store, because an LSM-tree can support a wider variety of operations and show better performance, especially for writes. However, LSM-tree is difficult to implement in the resource constrained environment of a key-value SSD (KV-SSD), and, consequently, KV-SSDs typically use hash-based schemes. We present PinK, a design and implementation of an LSM-tree-based KV-SSD, which compared to a hash-based KV-SSD, reduces 99th percentile tail latency by 73%, improves average read latency by 42%, and shows 37% higher throughput. The key idea in improving the performance of an LSM-tree in a resource constrained environment is to avoid the use of Bloom filters and instead, use a small amount of DRAM to keep/pin the top levels of the LSM-tree. We also find that PinK is able to provide a flexible design space for a wide range of KV workloads by leveraging the read-write tradeoff in LSM-trees. © 2021 Association for Computing Machinery.1

Probability-based Address Translation for Flash SSDs

Thanks to the advance of NAND scaling technologies, an ultra-scale SSD (e.g., >> 100 TB) is introduced to markets. This rapid increase of SSD capacity, however, comes at the cost of more DRAM which resides in an SSD controller for logical-to-physical (L2P) address translation. Many have proposed various address translation algorithms to reduce DRAM, but they fail to provide short read latency, in particular when a workload has weak locality. This letter proposes a novel probability-based address translation algorithm, called ProbFTL. In contrast to existing translation techniques that maintain exact L2P mapping, ProbFTL employs a probability-based data structure, a bloom filter, for address translation. By leveraging a space-efficient nature of a bloom filter, ProbFTL reduces the amount of DRAM for address translation to 20 percent of the existing techniques. The read latency of ProbFTL is not affected from locality of a workload; ProbFTL guarantees a read amplification factor of 1.1 even under a random read workload. ProbFTL exhibits slightly worse garbage collection efficiency, but its write amplification factor is maintained sufficiently low.1

Unilateral pulmonary artery agenesis manifested by hemoptysis in pregnancy

Unilateral pulmonary artery agenesis (UPAA) is a rare congenital anomaly which can be symptomatic or even asymptomatic. Most of patients with isolated UPAA have mild symptoms and it is difficult to be diagnosed, especially when abnormal findings of chest radiograph are the first presentation. It is often misdiagnosed and is not considered during differential diagnosis. To make a diagnosis of UPAA, various imaging modalities including chest radiograph, computed tomography (CT), and angiography are used. We report a 33-year-old woman in pregnancy presented recurrent hemoptysis whose CT was postponed due to her pregnancy. Although CT is a useful diagnostic tool, chest radiograph could be used instead in pregnancy suggesting UPAA with a lot of information. Keywords: Unilateral pulmonary artery agenesis, Hemoptysis, Chest radiograph

Modernizing File System through In-Storage Indexing

We argue that a key-value interface between a file system and an SSD is superior to the legacy block interface by presenting KEVIN. KEVIN combines a fast, lightweight, and POSIX-compliant file system with a key-value storage device that performs in-storage indexing. We implement a variant of a log-structured merge tree in the storage device that not only indexes file objects, but also supports transactions and manages physical storage space. As a result, the design of a file system with respect to space management and crash consistency is simplified, requiring only 10.8K LOC for full functionality. We demonstrate that KEVIN reduces the amount of I/O traffic between the host and the device, and remains particularly robust as the system ages and the data become fragmented. Our approach outperforms existing file systems on a block SSD by a wide margin – 6.2× on average – for metadata-intensive benchmarks. For realistic workloads, KEVIN improves throughput by 68% on average. © 2021 by The USENIX Association. All rights reserved

A rare case of numerous thoracolithiasis with chest discomfort

Thoracolithiasis is a rare benign condition with mobile free bodies in the pleural cavity. It is asymptomatic and mostly found incidentally. Up to our knowledge there is no report of symptomatic numerous thoracolithiasis. We report a very rare case of thoracolithiasis in a 36-year-old female with chest discomfort. Images from computed tomography presented a chain of small non-enhancing nodules in the left hemi-diaphragmatic pleura. Exploratory thoracoscopy was performed and twenty-five mobile pearl like thoracolithiasis were discovered. Histopathology showed extensive necrotic fatty tissue at its center surrounded by fibrosis. The patient was symptom-free after the surgical removal of numerous thoracolithiasis, suggesting thoracolithiasis was associated with chest discomfort. Keywords: Thoracolithiasis, Pleural stone, Pleurolith, Intrathoracic calculus, Intrapleural loose bod