14,720 research outputs found
A Cache Management Strategy to Replace Wear Leveling Techniques for Embedded Flash Memory
Prices of NAND flash memories are falling drastically due to market growth
and fabrication process mastering while research efforts from a technological
point of view in terms of endurance and density are very active. NAND flash
memories are becoming the most important storage media in mobile computing and
tend to be less confined to this area. The major constraint of such a
technology is the limited number of possible erase operations per block which
tend to quickly provoke memory wear out. To cope with this issue,
state-of-the-art solutions implement wear leveling policies to level the wear
out of the memory and so increase its lifetime. These policies are integrated
into the Flash Translation Layer (FTL) and greatly contribute in decreasing the
write performance. In this paper, we propose to reduce the flash memory wear
out problem and improve its performance by absorbing the erase operations
throughout a dual cache system replacing FTL wear leveling and garbage
collection services. We justify this idea by proposing a first performance
evaluation of an exclusively cache based system for embedded flash memories.
Unlike wear leveling schemes, the proposed cache solution reduces the total
number of erase operations reported on the media by absorbing them in the cache
for workloads expressing a minimal global sequential rate.Comment: Ce papier a obtenu le "Best Paper Award" dans le "Computer System
track" nombre de page: 8; International Symposium on Performance Evaluation
of Computer & Telecommunication Systems, La Haye : Netherlands (2011
Dynamic Virtual Page-based Flash Translation Layer with Novel Hot Data Identification and Adaptive Parallelism Management
Solid-state disks (SSDs) tend to replace traditional motor-driven hard disks in high-end storage devices in past few decades. However, various inherent features, such as out-of-place update [resorting to garbage collection (GC)] and limited endurance (resorting to wear leveling), need to be reduced to a large extent before that day comes. Both the GC and wear leveling fundamentally depend on hot data identification (HDI). In this paper, we propose a hot data-aware flash translation layer architecture based on a dynamic virtual page (DVPFTL) so as to improve the performance and lifetime of NAND flash devices. First, we develop a generalized dual layer HDI (DL-HDI) framework, which is composed of a cold data pre-classifier and a hot data post-identifier. Those can efficiently follow the frequency and recency of information access. Then, we design an adaptive parallelism manager (APM) to assign the clustered data chunks to distinct resident blocks in the SSD so as to prolong its endurance. Finally, the experimental results from our realized SSD prototype indicate that the DVPFTL scheme has reliably improved the parallelizability and endurance of NAND flash devices with improved GC-costs, compared with related works.Peer reviewe
Elevating commodity storage with the SALSA host translation layer
To satisfy increasing storage demands in both capacity and performance,
industry has turned to multiple storage technologies, including Flash SSDs and
SMR disks. These devices employ a translation layer that conceals the
idiosyncrasies of their mediums and enables random access. Device translation
layers are, however, inherently constrained: resources on the drive are scarce,
they cannot be adapted to application requirements, and lack visibility across
multiple devices. As a result, performance and durability of many storage
devices is severely degraded.
In this paper, we present SALSA: a translation layer that executes on the
host and allows unmodified applications to better utilize commodity storage.
SALSA supports a wide range of single- and multi-device optimizations and,
because is implemented in software, can adapt to specific workloads. We
describe SALSA's design, and demonstrate its significant benefits using
microbenchmarks and case studies based on three applications: MySQL, the Swift
object store, and a video server.Comment: Presented at 2018 IEEE 26th International Symposium on Modeling,
Analysis, and Simulation of Computer and Telecommunication Systems (MASCOTS
uFLIP: Understanding Flash IO Patterns
Does the advent of flash devices constitute a radical change for secondary
storage? How should database systems adapt to this new form of secondary
storage? Before we can answer these questions, we need to fully understand the
performance characteristics of flash devices. More specifically, we want to
establish what kind of IOs should be favored (or avoided) when designing
algorithms and architectures for flash-based systems. In this paper, we focus
on flash IO patterns, that capture relevant distribution of IOs in time and
space, and our goal is to quantify their performance. We define uFLIP, a
benchmark for measuring the response time of flash IO patterns. We also present
a benchmarking methodology which takes into account the particular
characteristics of flash devices. Finally, we present the results obtained by
measuring eleven flash devices, and derive a set of design hints that should
drive the development of flash-based systems on current devices.Comment: CIDR 200
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