5 research outputs found
Understanding System Characteristics of Online Erasure Coding on Scalable, Distributed and Large-Scale SSD Array Systems
Large-scale systems with arrays of solid state disks (SSDs) have become
increasingly common in many computing segments. To make such systems resilient,
we can adopt erasure coding such as Reed-Solomon (RS) code as an alternative to
replication because erasure coding can offer a significantly lower storage cost
than replication. To understand the impact of using erasure coding on system
performance and other system aspects such as CPU utilization and network
traffic, we build a storage cluster consisting of approximately one hundred
processor cores with more than fifty high-performance SSDs, and evaluate the
cluster with a popular open-source distributed parallel file system, Ceph. Then
we analyze behaviors of systems adopting erasure coding from the following five
viewpoints, compared with those of systems using replication: (1) storage
system I/O performance; (2) computing and software overheads; (3) I/O
amplification; (4) network traffic among storage nodes; (5) the impact of
physical data layout on performance of RS-coded SSD arrays. For all these
analyses, we examine two representative RS configurations, which are used by
Google and Facebook file systems, and compare them with triple replication that
a typical parallel file system employs as a default fault tolerance mechanism.
Lastly, we collect 54 block-level traces from the cluster and make them
available for other researchers.Comment: This paper is accepted by and will be published at 2017 IEEE
International Symposium on Workload Characterizatio
FlashAbacus: A Self-Governing Flash-Based Accelerator for Low-Power Systems
Energy efficiency and computing flexibility are some of the primary design
constraints of heterogeneous computing. In this paper, we present FlashAbacus,
a data-processing accelerator that self-governs heterogeneous kernel executions
and data storage accesses by integrating many flash modules in lightweight
multiprocessors. The proposed accelerator can simultaneously process data from
different applications with diverse types of operational functions, and it
allows multiple kernels to directly access flash without the assistance of a
host-level file system or an I/O runtime library. We prototype FlashAbacus on a
multicore-based PCIe platform that connects to FPGA-based flash controllers
with a 20 nm node process. The evaluation results show that FlashAbacus can
improve the bandwidth of data processing by 127%, while reducing energy
consumption by 78.4%, as compared to a conventional method of heterogeneous
computing. \blfootnote{This paper is accepted by and will be published at 2018
EuroSys. This document is presented to ensure timely dissemination of scholarly
and technical work.Comment: This paper is published at the 13th edition of EuroSy
Amber: Enabling Precise Full-System Simulation with Detailed Modeling of All SSD Resources
SSDs become a major storage component in modern memory hierarchies, and SSD
research demands exploring future simulation-based studies by integrating SSD
subsystems into a full-system environment. However, several challenges exist to
model SSDs under a full-system simulations; SSDs are composed upon their own
complete system and architecture, which employ all necessary hardware, such as
CPUs, DRAM and interconnect network. Employing the hardware components, SSDs
also require to have multiple device controllers, internal caches and software
modules that respect a wide spectrum of storage interfaces and protocols. These
SSD hardware and software are all necessary to incarnate storage subsystems
under full-system environment, which can operate in parallel with the host
system. In this work, we introduce a new SSD simulation framework, SimpleSSD
2.0, namely Amber, that models embedded CPU cores, DRAMs, and various flash
technologies (within an SSD), and operate under the full system simulation
environment by enabling a data transfer emulation. Amber also includes full
firmware stack, including DRAM cache logic, flash firmware, such as FTL and
HIL, and obey diverse standard protocols by revising the host DMA engines and
system buses of a popular full system simulator's all functional and timing CPU
models (gem5). The proposed simulator can capture the details of dynamic
performance and power of embedded cores, DRAMs, firmware and flash under the
executions of various OS systems and hardware platforms. Using Amber, we
characterize several system-level challenges by simulating different types of
fullsystems, such as mobile devices and general-purpose computers, and offer
comprehensive analyses by comparing passive storage and active storage
architectures.Comment: This paper has been accepted at the 51st Annual IEEE/ACM
International Symposium on Microarchitecture (MICRO '51), 2018. This material
is presented to ensure timely dissemination of scholarly and technical wor
Exploring Fault-Tolerant Erasure Codes for Scalable All-Flash Array Clusters
Large-scale systems with all-flash arrays have become increasingly common in
many computing segments. To make such systems resilient, we can adopt erasure
coding such as Reed-Solomon (RS) code as an alternative to replication because
erasure coding incurs a significantly lower storage overhead than replication.
To understand the impact of using erasure coding on the system performance and
other system aspects such as CPU utilization and network traffic, we build a
storage cluster that consists of approximately 100 processor cores with more
than 50 high-performance solid-state drives (SSDs), and evaluate the cluster
with a popular open-source distributed parallel file system, called Ceph.
Specifically, we analyze the behaviors of a system adopting erasure coding from
the following five viewpoints, and compare with those of another system using
replication: (1) storage system I/O performance; (2) computing and software
overheads; (3) I/O amplification; (4) network traffic among storage nodes, and
(5) impact of physical data layout on performance of RS-coded SSD arrays. For
all these analyses, we examine two representative RS configurations, used by
Google file systems, and compare them with triple replication employed by a
typical parallel file system as a default fault tolerance mechanism. Lastly, we
collect 96 block-level traces from the cluster and release them to the public
domain for the use of other researchers.Comment: 19 pages, 46 figures. arXiv admin note: substantial text overlap with
arXiv:1709.0536
Faster than Flash: An In-Depth Study of System Challenges for Emerging Ultra-Low Latency SSDs
Emerging storage systems with new flash exhibit ultra-low latency (ULL) that
can address performance disparities between DRAM and conventional solid state
drives (SSDs) in the memory hierarchy. Considering the advanced low-latency
characteristics, different types of I/O completion methods (polling/hybrid) and
storage stack architecture (SPDK) are proposed. While these new techniques are
expected to take costly software interventions off the critical path in
ULL-applied systems, unfortunately no study exists to quantitatively analyze
system-level characteristics and challenges of combining such newly-introduced
techniques with real ULL SSDs. In this work, we comprehensively perform
empirical evaluations with 800GB ULL SSD prototypes and characterize ULL
behaviors by considering a wide range of I/O path parameters, such as different
queues and access patterns. We then analyze the efficiencies and challenges of
the polled-mode and hybrid polling I/O completion methods (added into Linux
kernels 4.4 and 4.10, respectively) and compare them with the efficiencies of a
conventional interrupt-based I/O path. In addition, we revisit the common
expectations of SPDK by examining all the system resources and parameters.
Finally, we demonstrate the challenges of ULL SSDs in a real SPDK-enabled
server-client system. Based on the performance behaviors that this study
uncovers, we also discuss several system implications, which are required to
take a full advantage of ULL SSD in the future.Comment: 12 pages, 23 figures, 2019 IEEE International Symposium on Workload
Characterizatio