Partitioned Real-Time NAND Flash Storage Katherine Missimer and Rich - - PowerPoint PPT Presentation

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Partitioned Real-Time NAND Flash Storage Katherine Missimer and Rich - - PowerPoint PPT Presentation

Jan 06, 2024 281 likes •776 views

Partitioned Real-Time NAND Flash Storage Katherine Missimer and Rich West Introduction 2 Introduction 3 Introduction 4 NAND Flash Memory Non-volatility Shock resistance Low power consumption Fast access time 5 NAND Flash Memory No

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Partitioned Real-Time NAND Flash Storage

Katherine Missimer and Rich West

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Introduction

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Introduction

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Introduction

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NAND Flash Memory

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Non-volatility Shock resistance Low power consumption Fast access time

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NAND Flash Memory

Non-volatility Shock resistance Low power consumption Fast access time No in-place updates Reads & writes operate at different granularity than erasures

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SSD Internals

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SSD Internals

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SSD Internals

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SSD Internals

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SSD Internals

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Observations

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PaRT-FTL

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PaRT-FTL

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PaRT-FTL

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PaRT-FTL

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Buffered pages

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PaRT-FTL

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Buffered pages

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PaRT-FTL

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Buffered pages

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PaRT-FTL

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Buffered pages

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PaRT-FTL

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Buffered pages

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PaRT-FTL

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Buffered pages

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PaRT-FTL

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Buffered pages

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Real-Time Task Model

Parameters for a task:

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# pages in read request # pages in write request read period write period

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Real-Time Task Model

Parameters for a task:

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# pages in read request # pages in write request read period write period A task does not account for the CPU computation time. These tasks exist on the flash translation layer and utilize the NAND bus.

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Real-Time Task Model

Parameters for a task: Read capacity: Write capacity:

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# pages in read request time to read a page time to decode a page

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Real-Time Task Model

Parameters for a task: Read capacity: Write capacity:

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# pages in write request time to write a page # write chips

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Real-Time Task Model

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Real-Time Task Model

Encoding task when w > 0:

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time to write a page # pages per block # write chips time to encode a page

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Real-Time Task Model

Encoding task when w > 0:

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# pages per block # pages in write request write period

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Real-Time Task Model

Garbage collection task when w > 0:

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NAND Flash Memory Garbage Collection

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1. Write 3 flash pages of Logical Page Numbers (LPN): 0, 1, 2

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NAND Flash Memory Garbage Collection

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1. Write 3 flash pages of Logical Page Numbers (LPN): 0, 1, 2 2. Update LPN=0

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NAND Flash Memory Garbage Collection

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1. Write 3 flash pages of Logical Page Numbers (LPN): 0, 1, 2 2. Update LPN=0 3. GC triggered to reclaim Block 1000

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NAND Flash Memory Garbage Collection

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1. Write 3 flash pages of Logical Page Numbers (LPN): 0, 1, 2 2. Update LPN=0 3. GC triggered to reclaim Block 1000 4. Copy valid pages in victim block to a free block

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NAND Flash Memory Garbage Collection

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1. Write 3 flash pages of Logical Page Numbers (LPN): 0, 1, 2 2. Update LPN=0 3. GC triggered to reclaim Block 1000 4. Copy valid pages in victim block to a free block 5. Erase victim block

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Real-Time Task Model

Garbage collection task when w > 0:

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Over-provisioning

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Real-Time Task Model

Garbage collection task when w > 0:

Over-provisioning GC victim block

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Real-Time Task Model

time before the next block needs to be reclaimed

Garbage collection task when w > 0:

time spent copying valid pages and erasing the victim block

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Admission Control

Read set: Write set:

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Admission Control

Read set: Write set:

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minimum read period time to read a page

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Admission Control

Read set: Write set:

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minimum period in all write, encoding and GC tasks time to erase a block

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Admission Control Simulations

# of task sets: 500 # of tasks per task set: 10 Each task makes 1-page read and 3-page write requests per period Periods are calculated based on generated utilizations

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OpenSSD Cosmos Board

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Experimental Results: PaRT-FTL

8 tasks 4 tasks make write requests: 12-page writes every 60 msec 4 tasks make read requests: 3-page reads every 15 msec

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Write requests Read requests

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Experimental Results: WAO-GC

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Write requests Read requests 8 tasks 4 tasks make write requests: 12-page writes every 60 msec 4 tasks make read requests: 3-page reads every 15 msec

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Experimental Results

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Conclusion

Contributions of PaRT-FTL:

  • An FTL design that takes advantage of internal

parallelism in SSDs

  • A real-time task model for read and write requests on

multiple flash chips

  • Bounded and low-latency read requests that are not

blocked by write requests or garbage collection

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