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13 Νοε 2013 (πριν από 3 χρόνια και 9 μήνες)

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Flash
-
memories in
Space Applications:
Trends

and Challenges

Michele FABIANO


Paolo PRINETTO

Politecnico di Torino (Italy
)


Maurizio CARAMIA

Thales
Alenia

Space Italy

18
th



21
st

September 2009, EWDTS ’09

© Fabiano
-

2009

Goal


Exploring

Flash
-
memory

design

dimensions

and

trade
-
offs

for

flash
-
based

mass

memory

devices

for

space

applications

ExoMars

Mission

Aim
:


further characterize the
biological environment
on
Mars


preparation for robotic
and human exploration


gather data for
Exo
biology (
the search
for life on other planets
)

18
th



21
st

September 2009, EWDTS ’09

© Fabiano
-

2009

Outline


State of the art


Flash
-
memory peculiarities


Space Applications


Designing Flash
-
based hard
-
disks


Flash
-
based hard
-
disks for space
applications


Conclusions and future works

18
th



21
st

September 2009, EWDTS ’09

© Fabiano
-

2009

Outline


State

of

the

art


Flash
-
memory

peculiarities


Space

Applications


Designing

Flash
-
based

hard
-
disks


Flash
-
based

hard
-
disks

for

space

applications


Conclusions

and

future

works

18
th



21
st

September 2009, EWDTS ’09

© Fabiano
-

2009

State of the art


Space applications have:


always increasing
processing power


strict requirements

(e.g., power consumption,

weight, radiations hardening, dependability,
…)


A
mass memory device (i.e., an hard
-
disk) is
required


Flash
-
memories

can be used for this scope

18
th



21
st

September 2009, EWDTS ’09

© Fabiano
-

2009

Why Flash Memory?

Flash

Memories

are
:


Non
-
volatile
:

suitable

as

mass

memory

devices


Shock
-
resistant


Power
-
aware



-

less

energy

than

mechanical

devices



-

suitable

to

mobile

device





but

there

is

not

free

lunch!

18
th



21
st

September 2009, EWDTS ’09

© Fabiano
-

2009

Outline


State

of

the

art


Flash
-
memory

peculiarities


Space

Applications


Designing

Flash
-
based

hard
-
disks


Flash
-
based

hard
-
disks

for

space

applications


Conclusions

and

future

works

18
th



21
st

September 2009, EWDTS ’09

© Fabiano
-

2009

NAND Vs NOR

Flash
-
memories

in

the

current

market
:



NOR

flash
-
memories
:

low

density,

EEPROM

replacement

and

more

suitable

for

program

execution



NAND

flash
-
memories
:

high

density,

more

suitable

for

storage

systems

Blocks and pages
management

Flash
-
memories

are
:


partitioned

into

blocks


each

block

is

partitioned

into

pages


Operations
:


Read/write
:

pages


Erase
:

blocks

(i
.
e
.
,

all

the

pages

of

the

block)


Limitations
:


Blocks

wear

out

after

a

fixed

number

of

erasure

cycles

(i
.
e
.
,

actually

10
6
)

18
th



21
st

September 2009, EWDTS ’09

© Fabiano
-

2009

Outline


State

of

the

art


Flash
-
memory

peculiarities


Space

Applications


Designing

Flash
-
based

hard
-
disks


Flash
-
based

hard
-
disks

for

space

applications


Conclusions

and

future

works

18
th



21
st

September 2009, EWDTS ’09

© Fabiano
-

2009

Taxonomy


Vast

quantity

of

design

parameters


A

(complete)

taxonomy

is

required

18
th



21
st

September 2009, EWDTS ’09

© Fabiano
-

2009

Flash
-
memory

Technology


NAND

Vs

NOR
:

the

most

suitable

choice

is

NAND

technology

for

mass

memory

devices

18
th



21
st

September 2009, EWDTS ’09

© Fabiano
-

2009

Flash
-
memory

Architecture


Defining

blocks

and

pages


Selecting

the

most

appropriate

chipset

18
th



21
st

September 2009, EWDTS ’09

© Fabiano
-

2009

Flash
-
memory
Dependability


Several

critical

issues,

strictly

linked

together


18
th



21
st

September 2009, EWDTS ’09

© Fabiano
-

2009

Flash Memory

Testing

Different

from

other

memory

testing,

both

RAM

and

ROM,

because

of

peculiar
:


Failure

modes


Architecture

and

way

of

working




p
牯灥r

瑥獴

慬杯物a桭h

慲a

湥敤敤n

18
th



21
st

September 2009, EWDTS ’09

© Fabiano
-

2009

Wearing

Apart

from

definitions,

the

main

point

is

that


Flash Memories DO NOT live
forever!!!



Flash

Memory

wears

out


Limited

number

of

erase

cycles




proper

strategies

are

needed
!

18
th



21
st

September 2009, EWDTS ’09

© Fabiano
-

2009

Wear Leveling


Main

idea
:

distributing

data

evenly

across

each

memory

block



it

decreases

the

total

wear

on

the

drive


it

increases

the

lifetime

of

the

drive
:

no

single

erase

block

prematurely

fails

due

to

a

high

concentration

of

write

cycles



Several

interesting

techniques

have

been

proposed

and

the

field

is

very

active

18
th



21
st

September 2009, EWDTS ’09

© Fabiano
-

2009

Garbage Collection


Free
-
space

is

going

to

run

out


Invalidated

pages

(i
.
e
.
,

garbage)

have

to

be

erased


The

only

way

to

erase

them

is

to

erase

the

whole

block

they

belong

to


Valid

pages

of

the

block

need

to

be

kept

safe

18
th



21
st

September 2009, EWDTS ’09

© Fabiano
-

2009

Bad Block

Management


Bad

blocks

come

out

because
:



blocks

exceed

the

maximum

number

of

erasure

cycles


NAND

Flash

already

contains

some

bad

blocks



In

both

cases,

bad

blocks

have

to

be

detected

and

excluded

from

active

memory

space

18
th



21
st

September 2009, EWDTS ’09

© Fabiano
-

2009

Flash
-
based Hard
-
disk

Management


Challenging

aspects

regarding

Operating

Systems

(OS),

etc
.

18
th



21
st

September 2009, EWDTS ’09

© Fabiano
-

2009

Address Translation


Invalid

data

are

just

marked

as

not

valid,

while

the

garbage

collection

process

will

delete

them

(i
.
e
.
,

Out
-
place

Updating
)


Only

physical

addresses

of

data

should

be

revised


18
th



21
st

September 2009, EWDTS ’09

© Fabiano
-

2009

Operating System

Management


OS

were

developed

to

communicate

with

“usual”

magnetic

hard
-
disks



NAND

flash
-
memories

are

a

new

class

of

mass
-
memory

devices

18
th



21
st

September 2009, EWDTS ’09

© Fabiano
-

2009

Operating System

Management

(cont’d)


Proper

solutions

are

needed

in

order

to

let

OS

successfully

communicate

with

NAND

flash
-
memory

devices,

typically
:


block

device

emulation,

for

compatibility

reasons

(i
.
e
.
,

FAT,

NTFS)
;


native

flash

file

system,

for

dependability

reasons

(i
.
e
.
,

JFFS
2
,

YAFFS)

18
th



21
st

September 2009, EWDTS ’09

© Fabiano
-

2009

Outline


State of the art


Flash
-
memory peculiarities


Space Applications


Designing Flash
-
based hard
-
disks


Flash
-
based hard
-
disks for space applications


Conclusions and future works

18
th



21
st

September 2009, EWDTS ’09

© Fabiano
-

2009

Flash
-
based HDs for

Space Applications

Typical

constraints

in

terms

of
:



Weight
:

physical

weight


Cost


Bandwidth
:

throughput

of

the

system


Dependability


Never

losing

data
:

e
.
g
.
,

if

power

suddenly

goes

down




18
th



21
st

September 2009, EWDTS ’09

© Fabiano
-

2009

Flash
-
based
HDs

for

Space Applications
(
cont’d)





Mass

Memory

shall

provide

at

least

X

GByte

of

non
-
volatile

memory

capacity

at

End
-
Of
-
Life

(EOL)


Vendors

should

provide

flash
-
memories

physically

qualified

to

survive

in

the

space

environment




18
th



21
st

September 2009, EWDTS ’09

© Fabiano
-

2009

Outline


State

of

the

art


Flash
-
memory

peculiarities


Space

Applications


Designing

Flash
-
based

hard
-
disks


Flash
-
based

hard
-
disks

for

space

applications


Conclusions

and

future

works

18
th



21
st

September 2009, EWDTS ’09

© Fabiano
-

2009

Conclusions


Flash
-
memories

are

non
-
volatile
,

shock
-
resistant

and

power

aware



Space

applications

requirements

nicely

fit

with

flash
-
memory

characteristics



Designers

have

to

carefully

address

the

several

challenges

and

drawbacks

out
-
coming

by

using

Flash
-
memory

devices

18
th



21
st

September 2009, EWDTS ’09

© Fabiano
-

2009

On
-
going

Work


We

are

implementing

FLARE
:

a

powerful

design

environment

for

supporting

designers

of

a

flash
-
based

mass
-
memory

device

for

space

applications
.

18
th



21
st

September 2009, EWDTS ’09

© Fabiano
-

2009

Малые Автюхи, Калинковичский район
,
Республики Беларусь

C
па
c
иб
o

!!!