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

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 in-place updates Non-volatility Reads & writes operate at Shock resistance different granularity than Low power erasures consumption Fast access time 6

SSD Internals 7

SSD Internals 8

SSD Internals 9

SSD Internals 10

SSD Internals 11

Observations 12

PaRT-FTL 13

PaRT-FTL 14

PaRT-FTL 15

PaRT-FTL Buffered pages 16

PaRT-FTL Buffered pages 17

PaRT-FTL Buffered pages 18

PaRT-FTL Buffered pages 19

PaRT-FTL Buffered pages 20

PaRT-FTL Buffered pages 21

PaRT-FTL Buffered pages 22

Real-Time Task Model Parameters for a task: # pages in read # pages in write read request period write request period 23

Real-Time Task Model Parameters for a task: # pages in read # pages in write read request period write request period A task does not account for the CPU computation time. These tasks exist on the flash translation layer and utilize the NAND bus. 24

Real-Time Task Model Parameters for a task: Read capacity: Write capacity: # pages in time to time to read request read a page decode a page 25

Real-Time Task Model Parameters for a task: Read capacity: Write capacity: # pages in time to write # write write request a page chips 26

Real-Time Task Model 27

Real-Time Task Model Encoding task when w > 0: time to encode a page # pages per # write time to write block chips a page 28

Real-Time Task Model Encoding task when w > 0: # pages per block write # pages in period write request 29

Real-Time Task Model Garbage collection task when w > 0: 30

NAND Flash Memory Garbage Collection 1. Write 3 flash pages of Logical Page Numbers (LPN): 0, 1, 2 31

NAND Flash Memory Garbage Collection 1. Write 3 flash pages of Logical Page Numbers (LPN): 0, 1, 2 2. Update LPN=0 32

NAND Flash Memory Garbage Collection 1. Write 3 flash pages of Logical Page Numbers (LPN): 0, 1, 2 2. Update LPN=0 3. GC triggered to reclaim Block 1000 33

NAND Flash Memory Garbage Collection 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 34

NAND Flash Memory Garbage Collection 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 35

Real-Time Task Model Garbage collection task when w > 0: Over-provisioning 36

Real-Time Task Model Garbage collection task when w > 0: Over-provisioning GC victim block 37

Real-Time Task Model Garbage collection task when w > 0: time spent copying valid pages and erasing the victim block time before the next block needs to be reclaimed 38

Admission Control Read set: Write set: 39

Admission Control time to Read set: read a page minimum read period Write set: 40

Admission Control Read set: time to Write set: erase a block minimum period in all write, encoding and GC tasks 41

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 42

OpenSSD Cosmos Board 43

Experimental Results: PaRT-FTL 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 44

Experimental Results: WAO-GC 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 45

Experimental Results 46

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 47