Upload
flashdomain
View
194
Download
0
Tags:
Embed Size (px)
Citation preview
The Behavior Analysis of Flash Memory Storage
Systems
The Behavior Analysis of Flash Memory Storage
Systems
Po-Chun Huang, Yuan-Hao Chang, Tei-Wei Kuo, Jen-Wei Hsieh
Dept. of Comp. Sci. & Info. Engr.National Taiwan University, Taiwan
Agenda
Introduction
Flash-Memory Characteristics
Behavior Analysis
Conclusion
April 12, 2023 2
Introduction – Why Flash Memory
Diversified Application Domains
April 12, 2023 3
Mobile Media Players
Mobile Media Players
Solid-State Disks (SSD)
Solid-State Disks (SSD)
Thumb Disks
Thumb Disks
Multimedia Memory Cards
Multimedia Memory Cards
Embedded Systems
Embedded Systems
Introduction – NAND-Type Flash Makers
http://hugoleijtens.spaces.live.com/blog/cns!4B94B7453D4BFD9E!988.entry
Source: iSuppli Corp (Unit: Million Dollars)
[EE Times,11/30/2007] NAND flash prices have dropped by an average of more than 40 % per year.
5
Flash Memory Characteristics – A Typical Architecture
……
Block 0
Block 1
Block 2
Block 3
Erase one blockErase one block
1 Page = 2KB1 Block = 64 pages(128KB)
……
Write one pageWrite one page
6
Flash Memory Characteristics –Access ConstraintsWrite-Once
– No writing on the same page unless its residing block is erased!
– Pages are classified into valid, invalid, and free pages.
Bulk-Erasing – Pages are erased in a block unit to recycle used but
invalid pages.
Wear-Leveling– Each block has a limited lifetime in erasing counts.
Flash Memory Characteristics – NOR-type & NAND-type
NOR-type NAND-type
Access Unit Byte (Random Read, Sequential Write)
Page (Serial Access)
Cost Higher Lower
XIP Support Yes No
Write 8MB/s 20MB/s
PurposeXIP media (such as EPROM, EEPROM, EAROM, and DRAM)
Nonvolatile secondary storage media (such as Hard disk)
April 12, 2023 7
Flash Memory Characteristics – Small and Large Block Flash MemoryFlash memory page and block sizes are growing
April 12, 2023 8
Small Block Large Block
Page Size 512+16 Bytes 2K~8K Bytes
Block Size 16K Bytes 128K~256K Bytes
Used for... <1G Bytes >1G Bytes
Throughput Low High
Small Block Now Switches to Large Block
Introduction (cont’d)Single-Level-Cell and Multi-Level Cell Flash Memory
MLC has gained its momentum in cost and capacity!
April 12, 2023 9
SLC Flash MLC Flash
Cell Level 1 2 or 4
Cost 17.2 USD / 16G Bytes 5.25 USD / 16G Bytes
Chip Density Lower Higher
Access Speed Higher Lower
Average Cell Endurance 104~105 W-E cycles* 103~104 W-E cycles
Partial Programming Yes (4 times) No (1 time)
Sequential Utilization Constraint of Pages in a Block No Yes
*Write-Erase Cycles
Flash-Memory Characteristics – Hard Disks versus Flash Memory
April 12, 2023 10
Hard Disk (NAND-type) Flash Memory
Access Granularity Page-based Access Page-based Access
Write-once No Yes
Erasure No Need to Erase Bulk Erasure
Medium Lifetime Very Long Median
Cost Lower Higher
Other Properties and Constraints
•Long seek time and rotational latency•Power-hunger•Spin-up latency
•Shock resistance•High density
Flash-Memory Characteristics – System ArchitectureIn order to address the special properties and constraints of flash
memory, a good management scheme is required
Typical forms of management schemes are implemented as the Flash Translation Layer (FTL), the driver, or the Flash File System (FFS), each with different design considerations
April 12, 2023 11
Flash-Memory Characteristics – System ArchitectureA Typical Flash Memory Management Scheme
April 12, 2023 12
Perform Address Translation from LBA to PBA
Perform Address Translation from LBA to PBA
Determine the Physical Position of Written Data
Determine the Physical Position of Written Data
Because of the Write-Once Property, We Must Perform Garbage Collection Task to Released the Space Occupied by Invalidated Data
Because of the Write-Once Property, We Must Perform Garbage Collection Task to Released the Space Occupied by Invalidated Data
Garbage Collector Requires This Facility
Garbage Collector Requires This Facility
Even the Times of Utilization of Each Block to Avoid Fast Corruption
Even the Times of Utilization of Each Block to Avoid Fast Corruption
Behavior Analysis – Motivation
Physical properties of flash memory are very different from those of hard drives.
The management schemes give flash-memory storage systems special behaviors, compared to in-place update policies of many other storage systems.
There are few benchmarking tools with the considerations of the physical properties and the management schemes of flash memory.
April 12, 2023 13
Behavior Analysis – MotivationViews of a Flash Memory Storage System
April 12, 2023 14
User-PerspectiveUser-Perspective
Architecture-Perspective
Architecture-Perspective
Hardware-Perspective
Hardware-Perspective
Operation response time or throughput, product functional life span, file system operation latencies, prices, and compatibility
Operation response time or throughput, product functional life span, file system operation latencies, prices, and compatibility
Maintenance resources, assembly costs, architecture, and mediation between user expectation, hardware functions, and the flash management scheme
Maintenance resources, assembly costs, architecture, and mediation between user expectation, hardware functions, and the flash management scheme
production costs, materials, technology, cell reliability, etc.
production costs, materials, technology, cell reliability, etc.
Behavior Analysis – MotivationRevisiting of Existing I/O benchmarks
– IOZone: a file system benchmark considering no flash properties (http://www.iozone.org/)
– IOMeter: synthetic benchmark that users can control the degree of random-sequential access mixture. Does not consider flash properties (http://www.iometer.org)
– The effective I/O bandwidth benchmark: examine the I/O bandwidth achievable of an I/O device (http://www.hlrs.de/organization/par/services/models/mpi/b_eff_io/index_v1.2.html)
– IOBench: An operating system and processor independent synthetic input/output (IO) benchmark designed to put a configurable IO and processor (CP) load on the system under test (http://portal.acm.org/citation.cfm?id=71302.71309)
– Bonnie++: a benchmark suite that is aimed at performing a number of simple tests of hard drive and file system performance (http://www.coker.com.au/bonnie++/)
April 12, 2023 15
Behavior Analysis – Motivation
Unfortunately,–Physical properties of flash memory are different
from hard drives
–There are few benchmarking tools including the consideration of the management schemes of flash memory storage systems
–All previous works are based on user-perspective and consider no flash-specific properties and management overheads
April 12, 2023 16
Behavior Analysis
We need an evaluation strategy considering both the user and system architecture’s perspectives, so that–Users can fairly evaluate the cost-effectiveness
of various flash products
–System architects can have a fair method to evaluate their designs on architectures or the flash management schemes
April 12, 2023 17
The Behavior AnalysisOur Approach
–Micro-benchmark: evaluate specific metrics (instead of the overall status) of the system
- Best-case throughput
- Worst-case response time
–Macro-benchmark: probe the actual macroscopic behaviors of the systems- Read disturbance effects
- Write disturbance effects
- Simulation of actual traces
April 12, 2023 18
The Behavior AnalysisBest-Case Throughput Test: It is to examine the maximum possible performance of the device– Large, sequential accesses yield the best performance on
many FTLs
April 12, 2023 19
ith access
LBA Largest request packet length (1024 sectors on Windows; 128 sectors on USB interface)
The Behavior AnalysisWorst-Case Response Time Test: It is to examine the real-time access capability of a device– Small, random accesses yield the worst performance on
many FTLs
April 12, 2023 20
LBALBA
iithth access access
The Behavior AnalysisRead-Disturb Effect Test: It is to test the management
overheads about the read-disturb effect– Repetitively read a small range of data to examine the write
disturbance overhead– The first phase is only used to write the data that will be read later
April 12, 2023 21
LBA
ith access
Phase-1(Preparation)
Phase-2(Actual Test)
Hot area(test area)
Write the data for Future Read
Write the data for Future Read
Monitor the Performance Drop Continuously
Monitor the Performance Drop Continuously
Fill the Cache with Irrelevant Data to Avoid the Caching Effects
Fill the Cache with Irrelevant Data to Avoid the Caching Effects
The Behavior AnalysisWrite-Disturb Effect Test: It is to test the management
overheads about the write-disturb effect– Repetitively write to a small range of data to examine the write-disturb
overhead
– Accesses to other addresses are used to eliminate the caching effect
April 12, 2023 22
LBA
ith access
Hot area(test area)
Hot area(test area)
The Behavior AnalysisMultimedia environment: multimedia cards, thumb disks,
and SSDs are often used to keep multimedia contents– The contents of audio or video files are generally sequentially
accessed, while their metadata are randomly accessed
April 12, 2023 23
ith access
LBA
Metadata Area(Randomly Accessed)
Data Area(Sequentially Accessed)
Similar to the Behaviors of FAT
Similar to the Behaviors of FAT
The Behavior AnalysisMultiplexed environment: A large number of different
applications mixed together in multi-purpose systems – The behaviors are affected by a large number of factors, forming a
pattern following normal distribution
April 12, 2023 24
LBA
ith access
Random Starting Address
Random Starting Address
Random Access Length
Random Access Length
About the Timing of Request IssuingThe time intervals between consecutive requests matters– Foreground management
- Handle the requests on-demand
- Introduce user-sensible delays
– Background management- Handle some management tasks on system idle time
- Is not always applicable; for example, read requests must be served on-demand
If the interval between requests is large, background management will yield better performance, while foreground won’t
April 12, 2023 25
Conclusion and Future Work
Conclusion– In this paper, we provide a fair evaluation strategy for
flash memory storage systems so that- Users can evaluate the cost-effectiveness of various flash
products- Designers can evaluate the pros and cons of their designs and
improve them
Future Work– Investigate the relationship among different access
patterns, system architectures, and flash memory management schemes
– Analysis the access patterns of various applications of flash memory in the next generation
April 12, 2023 26
Contact Information
Po-Chun Huang, Ph.D. Student – Advisor: Prof. Tei-Wei Kuo
– Mail & MSN: [email protected]
– Flash Research Group: http://newslab.csie.ntu.edu.tw/~flash/
– Office: +886-2-33664888#438
– Fax: +886-2-23628167
– Address: Dept. of Computer Science & Information Engr.National Taiwan University, Taipei, Taiwan 106
April 12, 2023 27
Q & A
April 12, 2023 28