8. Multimedia File Systems

8. M

ultim

edia

File

Sys

tem

sMultimedia Kommunikation SS‘99

1 / 5

1C

onte

nts

8.1

Mot

ivat

ion

- W

hy M

ultim

edia

File

Sys

tem

s?8.

2 T

radi

tiona

l File

Sys

tem

s–

File

Str

uctu

re–

Per

form

ance

Con

side

ratio

n of

File

Str

uctu

re–

Dire

ctor

y S

truc

ture

–D

isk

Man

agem

ent

–D

isk

Sch

edul

ing

8.3

Mul

timed

ia F

ile S

yste

m–

Rea

l Tim

e C

hara

cter

istic

s8.

4 St

orag

e D

evic

es–

File

Str

uctu

re a

nd P

lace

men

t on

Dis

k–

Dis

k S

ched

ulin

g A

lgor

ithm

s–

Dat

a S

truc

turin

g8.

5 Sy

stem

Arc

hite

ctur

e–

UN

IX-b

ased

Sys

tem

s–

IBM

OS

2

8. M

ultim

edia

File

Sys

tem


2 / 5

18.

1 M

otiv

atio

n -

Why

Mul

timed

ia F

ile S

yste

ms?

Het

erog

eneo

us D

ata

Typ

es in

clud

ing

digi

tal a

udio

, ani

mat

ions

and

vid

eo

Con

sum

ing

enor

mou

s sp

ace

and

band

wid

th

(JPE

G-c

ompr

esse

d m

ovie

can

req

uire

ove

r 2

GB

yte)

Del

ay-s

ensi

tive:

whe

n us

er p

lays

-out

or

reco

rds

a tim

e de

pend

ent m

ultim

edia

data

obj

ect,

the

syst

em m

ust c

onsu

me

or p

rodu

ce a

t a c

onst

ant d

ata

gap-

free

rate

Í A

new

mul

timed

ia f

ile s

yste

m is

nee

ded

8. M

ultim

edia

File

Sys

tem


3 / 5

18.

2 T

radi

tiona

l File

Sys

tem

s

File

Sys

tem

is th

e m

ost v

isib

le p

art o

f an

Ope

ratin

g Sy

stem

and

con

sist

of:

1. F

iles

: Pro

gram

Cod

es

2. D

irec

tory

Str

uctu

re

: O

rgan

izes

file

s an

d pr

ovid

es in

form

atio

n, e

.g.

-rwxr-xr-x 1 root other 55160 Jul7 1995 gcc*

Tra

ditio

nal F

iles

: exe

cuta

bles

of

prog

ram

s,nu

mer

ic d

ata,

text

, obj

ects

etc

.

Goa

ls:

– P

rovi

de a

com

fort

able

inte

rfac

e fo

r fil

e ac

cess

– M

ake

effic

ient

use

of s

tora

ge m

edia

root

8. M

ultim

edia

File

Sys

tem


4 / 5

18.

2 T

radi

tiona

l File

Sys

tem

s / F

ile S

truc

ture

Non

-con

tiguo

us P

lace

men

t

Con

tiguo

us P

lace

men

t

1st f

ile2n

d fi

le3r

d fi

le

1st f

ile2n

d fi

le3r

d fi

le

8. M

ultim

edia

File

Sys

tem


5 / 5

18.

2 T

radi

tiona

l File

Sys

tem

s / P

erfo

rman

ce C

onsi

dera

tion

of F

ile S

truc

ture

Sequ

entia

l Sto

rage

:–

Dis

c ac

cess

tim

e fo

r re

adin

g an

d w

ritin

g is

min

imze

d

–O

n ta

pe th

e on

ly p

ossi

ble

way

–M

ajor

dis

adva

ntag

e fo

r fil

e cr

eatio

n, d

elet

ion

and

size

mod

ifica

tion

Non

-seq

uent

ial S

tora

ge (

two

mai

n ap

proa

ches

):

Lin

ked

All

ocat

ion:

–F

ine

for

sequ

entia

l acc

ess

–R

ando

m a

cces

s is

cos

tly

Inde

xed

All

ocat

ion:

(sim

ilar

to li

nked

allo

catio

n, b

ut

“lin

ks“

are

stor

ed in

an

“inde

xblo

ck“)

–C

ompl

ex–

Per

form

ance

dep

ends

on

the

inde

xst

ruct

ure

and

size

of t

he fi

le

16

82

45

73

begi

nnin

g po

inte

r

(fir

st b

lock

is 1

)(n

ext b

lock

is 2

)

16

82

45

73

1 2 3 8 6

8. M

ultim

edia

File

Sys

tem


6 / 5

18.

2 T

radi

tiona

l File

Sys

tem

s / D

irec

tory

Str

uctu

re

Mos

t of

toda

y´s

oper

atin

g sy

stem

s pr

ovid

e tr

ee-s

tru

ctur

ed d

irec

tori

es.

spel

lbi

npr

ogra

ms

root

stat

mai

ldi

stfi

ndco

unt

hex

reor

der

pe

mai

l

prog

copy

prt

exp

reor

der

list

find

hex

coun

t

list

obj

spel

l

8. M

ultim

edia

File

Sys

tem


7 / 5

18.

2 T

radi

tiona

l File

Sys

tem

s / D

isk

Man

agem

ent

Dis

k ac

cess

is s

low

and

cos

tly -

maj

or b

ottle

neck

Tec

hniq

ues

redu

cing

ove

rall

disk

acc

ess

time:

Blo

ck c

ache

s

–re

duce

s th

e nu

mbe

r of

dis

k ac

cess

Red

uce

disk

arm

mot

ion

–R

educ

es th

e tim

e fo

r on

e di

sk a

cces

s

Pla

ce c

onse

cutiv

e bl

ocks

in a

n in

terle

aved

man

ner.

Map

pin

g T

able

s ar

e pl

aced

in th

e

mid

dle

of th

e di

sk.

Tab

les

and

the

corr

espo

ndin

g bl

ocks

are

plac

ed o

n th

e sa

me

cylin

der.

1. h

ead

mov

emen

t

2. w

ait u

ntil

data

app

ears

und

er th

e he

ad

Inte

rlea

ved

Stor

age

Non

-int

erle

aved

Sto

rage H

eads

may

rea

d in

par

alle

l

rr

Ave

rage

m

ovem

ent

of r

/4

Ave

rage

m

ovem

ent

of r

/2

trac

k

data

8. M

ultim

edia

File

Sys

tem


8 / 5

18.

2 T

radi

tiona

l File

Sys

tem

s / D

isk

Sche

dulin

g

Tot

al ti

me

to s

ervi

ce a

dis

k re

ques

t con

sist

of:

–S

eek

time,

hea

d po

sitio

ning

to a

ppro

pria

te tr

ack

(dia

met

er)

–La

tenc

y (r

otat

ion

time)

, tim

e to

find

the

bloc

k in

a tr

ack

–A

ctua

l dat

a tr

ansf

er ti

me

Tec

hniq

ue to

red

uce

dela

y:

S

eek

oper

atio

n Í

S

ched

ulin

g al

gori

thm

s

L

aten

cy

Í

F

ile a

lloca

tion

met

hods

Sequ

entia

l sto

rage

dev

ices

(e.

g. ta

pes)

hav

e no

sch

edul

ing

prob

lem

Delay

8. M

ultim

edia

File

Sys

tem


9 / 5

18.

2 D

isk

Sche

dulin

g / F

irst

-Com

e-Fi

rst-

Serv

ed (

FCFS

)

Serv

e re

ques

ts in

ord

er o

f ar

riva

l

- N

ot o

ptim

al Í

Hig

h av

erag

e se

ek

133

019

899

5131

1369

6313

017

3

i+2

i

i+1

Ove

rall

mov

emen

tFC

FS: 6

73

99 173

31 130

13 133

63 69

i i+1

i+2

Que

ue

order of successive requests

+ E

asy

to p

rogr

am+

Fai

r al

gori

thm

8. M

ultim

edia

File

Sys

tem


10 /

518.

2 D

isk

Sche

dulin

g / S

hort

est-

Seek

-Tim

e Fi

rst (

SSFT

)

Serv

e “n

eare

st“

requ

est

Que

ue

99 173 31 130 13 133 63 69

Opt

imal

ove

rall

mov

emen

t: 19

8

133

019

899

5131

1369

6313

017

3

+ S

ubst

antia

l im

prov

emen

t ove

r FC

FS-

Still

not

opt

imal

- St

arva

tion

(of

som

e tr

acks

if th

ere

is a

lway

s a

trac

k w

ith s

hort

er s

eek

time

avai

labl

e)

(99

,48

)(

173,

122)

(31

,20

)(

130,

20)

(13

0,79

)(

13,

28)

(13

3,82

)(

63,

12)

(69

,18

)

Tra

ck

Seek

Tim

e

8. M

ultim

edia

File

Sys

tem


11 /

518.

2 D

isk

Sche

dulin

g / S

CA

N

SCA

N =

ser

ve r

eque

sts

in o

ne d

irec

tion;

then

rev

erse

the

mov

emen

t

Mov

e fr

om o

ne e

nd to

the

othe

r, s

ervi

cing

eac

h re

ques

t on

the

way

.

Que

ue

99 173 31 130 13 133 63 69

019

899

5131

1369

6313

0133

173

Ove

rall

mov

emen

tSC

AN

: 224

(las

t tra

ck 1

73)

Hea

d St

art

8. M

ultim

edia

File

Sys

tem


12 /

518.

2 D

isk

Sche

dulin

g / C

ircu

lar-

SCA

N

+ F

air

serv

ice

- m

ore

unif

orm

wai

ting

time

- Pe

rfor

man

ce n

ot a

s go

od a

s SC

AN

mid

dle

trac

ks d

on´t

get

a b

ette

r se

rvic

e th

an e

dge

trac

ks (

such

as

with

SC

AN

or

with

SS

TF

)

Sim

ilar

to S

CA

N b

ut r

etur

ns im

med

iatly

to th

e be

ginn

ing

if th

e en

d is

rea

ched

Que

ue

019

899

5131

1369

6313

0133

173

99 173 31 130 13 133 63 69

Ove

rall

Mov

emen

tC

-SC

AN

: 376

8. M

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edia

File

Sys

tem


13 /

518.

3 M

ultim

edia

File

Sys

tem

Req

uire

men

ts o

f co

ntin

uous

dat

a:

Rea

l Tim

e C

hara

cter

istic

:–

Con

stan

t gap

-fre

e ra

te Í

Add

ition

al b

uffe

rs

File

Siz

e:–

Hig

hly

stru

ctur

ed d

ata

units

(e.

g. v

ideo

and

ass

ocia

ted

audi

o)

Í N

ew o

rgan

izat

ion

polic

ies

of th

e da

ta o

n di

sk

–E

ffici

ent u

sage

of l

imite

d st

orag

e is

nec

essa

ry

Mul

tipl

e da

ta S

trea

m:

–F

or e

xam

ple:

ret

rieva

l of a

mov

ie r

eqire

s th

e pr

oces

sing

and

syn

chro

niza

tion

ofau

dio

and

vide

o

8. M

ultim

edia

File

Sys

tem


14 /

518.

3 M

ultim

edia

File

Sys

tem

/ R

equi

rem

ent o

f di

gita

l aud

io P

layb

ack

Bas

ic to

any

pla

ybac

k of

del

ay-s

ensi

tive

mul

timed

ia d

ata

Buf

fer

Stor

age

Aud

io H

ardw

are

uneq

ual t

imes

betw

een

succ

essi

ve d

ata

units

equa

l tim

es

betw

een

succ

essi

ve u

nits

Dat

a-R

etri

eval

Rat

e

+

C

onsu

mpt

ion

Rat

e

Buf

fer

Spac

e re

quir

emen

ts

8. M

ultim

edia

File

Sys

tem


15 /

518.

3 M

ultim

edia

File

Sys

tem

/ R

eal T

ime

Cha

ract

eris

tics

t r

R(t

)

t

Rea

ding

t

Play

back

# s a m p l e st 0

B(t

, t0)

= R

(t)-

C(t

, t0)

C(t

, t0)

R(t

)

R(t

) T

otal

num

ber

of s

ampl

es r

ead

up to

tim

e t

t r R

eadi

ng is

com

plet

edt 0

Pla

ybac

k st

arts

to u

se th

e di

gita

l to

anal

og c

onve

rter

C(t

, t0)

Num

ber

of c

onsu

med

sam

ples

up to

tim

e t r

C R

ate

of c

onsu

med

sam

ples

Con

sum

ptio

n or

der

and

phys

ical

pla

cem

ent a

re k

now

n Í

Opt

imal

for

buf

fer

requ

irem

ents

and

thro

ughp

ut

If R

(t)

> C

(t, t

0)

Í

Buf

fer

is n

eede

dR

(t)

≥ C

(t, t

0) r

equi

red

for

B(t

, t0)

:= R

(t)

- C

(t, t

0)ga

p-fr

ee p

layb

ack

Í F

ind

the

min

imum

buf

fer

size

0! )

()

,(

00

≥−

⋅=

tt

rt

tC

c

–W

e w

ant t

o h

ave:

–a

play

back

to

beg

in a

s ea

rly

as p

ossi

ble

–a

sma

ll b

uff

er

size

8. M

ultim

edia

File

Sys

tem


16 /

518.

3 M

ultim

edia

File

Sys

tem

/ R

eal T

ime

Cha

ract

eris

tics

“the

ear

lier

the

first

sam

ple

is p

laye

d ou

t, th

e le

ss b

uffe

r re

quir

emen

t“

t

# s a m p l e st 0

B(t

, t0)

R(t

)

t r

The

orem

1:

The

sol

utio

n us

ing

the

min

imum

sta

rt ti

me

for

play

back

also

req

uire

s th

e le

ast b

uffe

r sp

ace

at a

ny p

oint

in ti

me.

PRO

OF:

Let

t w b

e a

give

n so

lutio

n of

the

min

imum

sta

rt

time Í

Sho

w m

inim

um b

uffe

r si

ze.

+

−→

≥−

−<

=W

CC

WW

C

Ww

tr

tr

tR

tt

tt

rt

R

tt

tR

tt

B)

( )

()

(

)

()

,(

+

−→

≥−

−<

=y

rt

rt

Ry

ty

tr

tR

yt

tR

tt

BC

CC

w)

( )

()

(

)

()

,(

In g

ener

al:

yr

tr

CW

C≤

B(t

, tw)

≤ B

(t,y

)

8. M

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tem


17 /

518.

3 M

ultim

edia

File

Sys

tem

/ R

eal T

ime

Cha

ract

eris

tics

The

orem

2:

The

min

imum

val

ue f

or t 0

may

be

foun

d as

fol

low

s: c

onsi

der

B(t

,0)

1. I

f B

(t, 0

) ≥

0 fo

r 0

≤ t ≤

t r Í

t 0 =

0 is

the

solu

tion

2. -

m :=

min

(B

(t,0

)) a

t tim

e t m

in Í

B(t

min

, 0)

= -

m

The

inte

rsec

tion

of

R(t

) w

ith B

(t, 0

) +

m is

at t

i Í t 0

= t i

is th

e so

lutio

n yi

eldi

nga

wor

kabl

e pl

ayba

ck

t

B

t 0

B(t

, t0)

R(t

)

0

1.B

(t, 0

) +

m

t

B

R(t

)

-m2.

B(t

, 0)

t i

Sear

ch f

orB

(t, x

) w

ithB

(t, x

) ≥

0

0t

B(t

, 0)

x

}≥ m

8. M

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tem


18 /

518.

3 M

ultim

edia

File

Sys

tem

/ R

eal T

ime

Cha

ract

eris

tics

PRO

OF:

1. I

f B

(t, 0

) is

a a

solu

tion,

then

it m

ust b

e op

timal

acc

ordi

ng to

The

orem

1.

2. S

how

: eve

ry p

ossi

ble

solu

tion

b(t,

x) f

ulfi

ls th

e eq

uatio

n

B(t

, x)

- B

(t, 0

) ≥

m in

the

rang

e x

≤ t ≤

t rB

(t, 0

)=

R(t

) -

r Ct

B(t

, x)

= R

(t)

- r C

t + r

Cx

=

R(t

) -

r C(t

-x)

Í B

(t, x

) -

B(t

, 0)

= r

Cx=

con

st.

S

ame

slop

e, p

aral

lel

8. M

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tem


19 /

518.

3 M

ultim

edia

File

Sys

tem

/ R

eal T

ime

Cha

ract

eris

tics

How

to d

eter

min

e th

e co

nsta

nt r

cx?

t min

≥ x

Rem

embe

r B

(t,x

) ≥

0 fo

r 0

≤ t ≤

t r Í

B(t

min

,x)

≥ 0

with

B(t

min

,0)=

-m

(Sin

ce p

ossi

ble

solu

tion)

Í B

(tm

in,x

) -

B(t

min

,0)

≥ m

sinc

e B

(t,x

) pa

rall

el to

B(t

,0)

Í B

(t,x

) -

B(t

,0)

≥ m

for

x ≤

t ≤

t rt m

in<

x

R(t

) is

non

decr

easi

ng a

nd n

onne

gati

ve Í

R(t

min

) ≥

0 an

d B

(tm

in,0

) =

-m

sinc

e B

(t,x

) gr

ows

as R

(t)

does

in th

e ra

nge

of t m

in to

x a

nd B

(t,0

) on

ly a

s

R(t

) -

r ct t

he d

iffe

renc

e re

mai

ns a

t lea

st m

up

to ti

me

x.

i.e. B

(t,x

) -

B(t

,0)

≥ m

for

t min

≤ t

≤ x

and

even

for

x ≤

t ≤

t r, s

ince

B(t

,x)

para

llel

to B

(t,0

) fo

r t ≥

x.

8. M

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518.

3 M

ultim

edia

File

Sys

tem

/ R

eal T

ime

Cha

ract

eris

tics

Con

side

r B

(t,t i

) “t

i is

the

inte

rsec

tion

time

betw

een

R(t

) an

d B

(t,0

) +

m“

Sho

w: B

(t,t i)

is a

pos

sibl

e so

lutio

n.

Sh

ow

: t i i

s th

e m

inim

um p

layb

ack

star

t tim

e

≥

−−

≤=

mt

Bt

tt

tr

tR

tR

tt

tR

tt

Bi

ic

ii

by

)0,(

an

grea

ter

th

)(

)(

t to

up )(

as

sam

e

)

()

,(

i

B(t

i,ti)

= R

(t i)

= B

(t i,0

) +

m

B(t,

t i) ≥

0 f

or

0 ≤

t ≤ t r

is a

pos

sibl

e so

lutio

n

B(t

, 0)

+m

t

R(t

)

-mB

(t, 0

)

t it m

in

8. M

ultim

edia

File

Sys

tem


21 /

518.

3 M

ultim

edia

File

Sys

tem

/ R

eal T

ime

Cha

ract

eris

tics

Rem

embe

r: f

or a

ny s

olut

ion

hold

s B

(t,x

) ≥

B(t

,0)

+ m

in th

e ra

nge

x ≤

t ≤ t r

.

B(t

,t i)

has

the

smal

lest

con

stan

t dif

fere

nce

of a

ny s

olut

ion

(nam

ely

m)

Supp

ose

a so

lutio

n B

(t,y

) w

ith y

< t i

Í B

(tm

in,y

) <

B(t

min

,t i)=

0

Í t i

is th

e m

inim

um p

layb

ack

star

t tim

e Í

Buf

fer

not a

vaila

ble Í

con

trad

ictio

n

Rea

ding

sam

ples

in s

ecto

r un

it

How

to d

eter

min

e R

(t)?

Stor

age

devi

ces

read

dat

a in

sec

tors

e.g

. 512

byt

es

Var

ious

err

or c

orrr

ectio

n co

des

are

stor

ed w

ith

the

sect

or a

nd n

eed

the

com

plet

e se

ctor

bef

oreh

and

Í U

se th

e “n

umbe

r os

usa

ble“

func

tion

to fi

nd

the

min

imum

sta

rt ti

me

t Sect

or S

ize

# sa

mpl

es

Num

ber

of s

ampl

es r

ead

Num

ber

of s

ampl

es u

sabl

e

t 0, w

ith

t 0, w

itho

ut

p la

yout

cur

ve w

itho

utus

able

sam

ples

p la

yout

wit

h us

able

sam

ples

8. M

ultim

edia

File

Sys

tem


22 /

518.

4 St

orag

e D

evic

es

Tap

es a

re in

adeq

uate

for

mul

timed

ia s

yste

ms

Con

vent

iona

l mag

netic

sto

rage

dev

ices

are

not

suf

fici

ent (

may

not

be

up to

dat

e)

CD

-RO

Ms

are

ofte

n us

ed (

defi

ned

in I

SO 9

660)

Dis

cs c

an b

e cl

assi

fied

bas

ed o

n:

Stor

age

Met

hod

–R

e-w

ritab

le (

mag

netic

and

opt

ical

)

–W

rite-

once

(W

rite

Onc

e R

ead

Man

y, W

OR

M)

Phys

ical

med

ium

–M

agne

tic d

isk

(bet

ter

seek

tim

e)

–O

ptic

al d

isk

8. M

ultim

edia

File

Sys

tem


23 /

518.

4 St

orag

e D

evic

es /

File

Str

uctu

re a

nd P

lace

men

t on

Dis

k

Prov

ide

a co

nsta

nt a

nd ti

mel

y re

trie

val o

f da

ta:

–O

rgan

izat

ion

of fi

les

on d

isk

is o

ptim

ized

–A

dmis

sion

con

trol

is p

erfo

rmed

for

diffe

rent

ser

vice

cla

sses

–S

peci

al d

isk

sche

dulin

g al

gorit

hms

and

suffi

cien

t buf

fers

Prob

lem

: res

tric

ted

tran

sfer

rat

e

Con

tiguo

us P

lace

men

t–

Sim

ple

to im

plem

ent

/ S

ubje

ct to

frag

men

tatio

n–

Ove

rhea

d by

inse

rtio

n an

d de

letio

n–

Eas

y to

rea

d Í S

uita

ble

for

read

onl

ysy

stem

s–

Bui

ldin

g st

orag

e hi

erar

chie

–A

ddin

g te

rtia

ry s

tora

ge

Scat

tere

d Pl

acem

ent

–A

void

s fr

agm

enta

tion

–A

void

s co

pyin

g ov

erhe

ad–

See

k op

erat

ion

in w

orst

cas

e fo

r ea

chbl

ock

–Í

Add

ition

al b

uffe

ring

is n

eede

d

Man

agem

ent o

f di

sk s

tora

ge–

Opt

imal

pla

cing

of d

ata

bloc

ks o

n di

sk–

Usi

ng m

ultip

le d

isks

8. M

ultim

edia

File

Sys

tem


24 /

518.

4 St

orag

e D

evic

es /

Dis

k Sc

hedu

ling

Alg

orith

ms

Inte

rmed

iate

app

roac

h: c

onst

rain

ed p

lace

men

t

“bou

nds

the

sepa

ratio

n be

twee

n su

cces

sive

med

ia b

lock

s“

Par

amet

ers:

the

siz

e of

med

ia b

lock

(gr

anul

arity

par

amet

er G

)

# b

lock

s: s

epar

atio

n be

twee

n su

cces

sive

blo

cks

(sc

atte

ring

para

met

er S

)

Con

tinui

ty r

equi

rem

ent:

r D d

ata

tran

sfer

rat

e fr

om d

isk

r C p

layb

ack

rate

G

6 Se

cond

s fo

r 3

bloc

ks d

ata

S +

G

Í p

lay

back

rat

e: 0

.5

e.g.

G

= 3

r D =

2r C

= 0

,5(S

+3)

/2 ≤

3/0

.5S+

3 ≤

12S

≤ 9

CD

rG

r

GS

≤+pl

ayba

ck d

urat

ion

i.e. t

ime

to s

kip

over

a g

ap a

nd to

rea

d th

e te

xtm

edia

blo

ck is

sm

alle

r th

an o

r eq

ual t

o th

edu

ratio

n of

the

play

back

8. M

ultim

edia

File

Sys

tem


25 /

518.

4 St

orag

e D

evic

es /

Dis

k Sc

hedu

ling

Alg

orith

ms

Goa

ls in

Tra

diti

onal

File

Sys

tem

s (F

CFS

, SST

F, S

CA

N, C

-SC

AN

):–

Red

uce

cost

of s

eek

time

–A

chie

ve fa

ir th

roug

hput

–P

rovi

de fa

ir di

sk a

cces

s

Goa

ls in

Mul

tim

edia

File

Sys

tem

s:–

Mee

t dea

dlin

es o

f all

time-

criti

cal t

asks

–K

eep

the

nece

ssar

y bu

ffer

spac

e re

quire

men

ts lo

w

–F

ind

bala

nce

betw

een

time

cons

trai

nts

and

effic

ienc

y

8. M

ultim

edia

File

Sys

tem


26 /

518.

4 D

isk

Sche

dulin

g / E

arlie

st D

eadl

ine

Firs

t (E

DF)

Poo

r th

rouh

gput

due

to

exce

ssiv

e se

ek t

ime Í

Onl

y de

adlin

es a

re in

to a

ccou

nt, b

ut n

ot t

rack

num

ber.

Ver

y si

mila

r to

FC

FS:

inef

fici

ent

does

not

ref

lect

the

geo

grap

hica

l pos

itio

n of

tra

cks.

t3

24

330

316

350

342

345

312

340

322

112

240

122

2212

4540

4216

dead

line

trac

k no

.E

qual

dea

dlin

es Í

FC

FS

145

112

240

216

350

242

330

216

350

350

242

240

242

145

240

8. M

ultim

edia

File

Sys

tem


27 /

518.

4 D

isk

Sche

dulin

g / S

CA

N -

ED

F

Com

bina

tion

of:

–S

cann

ing

(per

form

ance

impr

ovem

ent b

y se

ekin

g “le

ft Í

rig

ht“

and

“rig

ht Í

left“

alte

rnat

ivel

y)

–D

eadl

ine

sche

dulin

g (s

ervi

ng e

arlie

r de

adlin

es fi

rst)

If de

dlin

es d

iffer

from

eac

h ot

her

then

the

stra

tegy

doe

s no

t wor

k w

ell s

ince

“S

CA

N“

ispr

actic

ally

use

less

.

Thu

s:

It ha

s to

be

enfo

rced

that

man

y re

ques

ts h

ave

the

sam

e de

adlin

e. W

e as

sum

e th

at a

llre

ques

ts a

re g

roup

ed in

a fe

w g

roup

s w

hich

can

be

scan

ned

toge

ther

.

Dea

dlin

es D i

are

mul

tiple

s of

a c

omm

on p

erio

d p Í

Di ∈

{1,

2, 3

, ...}

.

For

an

impl

enta

tion

of S

CA

N-E

DF

(i.e

. for

ser

ving

all

requ

ests

with

the

sam

e

dead

line

acco

rdin

g to

SC

AN

) w

e in

trod

uce

the

conc

ept o

f “de

adlin

e pe

rtur

batio

n“.

8. M

ultim

edia

File

Sys

tem


28 /

518.

4 D

isk

Sche

dulin

g / S

CA

N -

ED

F

Pert

urba

tion

of d

eadl

ines

(in

ord

er to

app

ly E

DF)

Let

Di t

he d

eadl

ine

of tr

ack

num

ber

Ni =

i (0

≤ N

i ≤ N

max

, e.

g. N

max

=10

0)

Ass

ume

that

Di ∈

N

Mod

ify

Di t

owar

ds D

i´ (D

i´= p

ertu

rted

dea

dlin

e)

Di´

= D

i·f(

Ni)

f(N

i) de

pend

s on

the

trac

k po

sitio

n of

task

i.

We

cho

ose

Thu

s if

the

dead

line

for

a ta

sk o

n tr

ack

42 is

equ

al to

3 th

en th

e pe

rtur

ted

dead

line

is

Thi

s de

adlin

e is

giv

en to

the

task

at a

rriv

al ti

me.

1)

(0

)(

max

<≤

⇒

=

iii

Nf

NNN

f

100

exam

ple

for

an

dm

ax=

=N

iN

i

D

i < D

j

Í D

i < D

j´

42,33

100

42=

+

8. M

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edia

File

Sys

tem


29 /

518.

4 D

isk

Sche

dulin

g / S

CA

N -

ED

F

Am

ong

the

sam

e de

adli

ne S

CA

N is

app

lied

Req

uest

wit

h th

e ea

rlie

st d

eadl

ine

is s

erve

d

Sen

sibl

e on

ly f

or a

larg

e nu

mbe

r of

req

uest

s

Opt

imiz

atio

n on

ly a

plli

es f

or r

eque

sts

wit

hth

e sa

me

dead

line

Incr

ease

this

pro

babi

lity

by

grou

ping

the

requ

ests

Í

t2.

1624

3.50

50

2.42

42

1.45

45

1.12

12

2.40

45

1.22

12

12

22

45

40

16

1.12

12

2.40

40

1.22

22

1.45

45

2.40

40

1.22

22

2.42

42

2.40

40

1.45

45

3.50

50

2.42

42

2.40

40

2.16

16

3.50

50

2.42

42

dead

line

1, i.

e. ∈

[1:

2]

dead

line

2, i.

e. ∈

[2:

3]

Nm

ax =

100

(hi

ghes

t tra

ck n

umbe

r)

Pert

ubat

ion

of D

eadl

ine

Tra

cknu

mbe

r

8. M

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edia

File

Sys

tem


30 /

518.

4 D

isk

Sche

dulin

g / E

DF,

SC

AN

-ED

F

010

2030

40

50

Deadlines

ED

FSC

AN

-ED

F

8. M

ultim

edia

File

Sys

tem


31 /

518.

4 D

isk

Sche

dulin

g

A s

mal

l var

iatio

n of

“de

adlin

e pe

rtur

batio

n“

The

act

ual d

eadl

ine

give

n to

the

task

is r

efin

ed b

y:–

taki

ng a

ccou

nt th

e ac

tual

mov

emen

t of t

he h

ead

at a

rriv

al ti

me

(i.e.

upw

ards

from

0 to

Nm

ax-1

or

dow

nwar

ds fr

om N m

ax-1

to 0

)

–a

nd c

onsi

derin

g th

e ac

tual

pos

ition

, n, o

f the

hea

d.

The

per

turb

ed d

eadl

ine

for

a ta

sk w

hich

res

ists

on

trac

k N

i is

give

n by

: D

i´= D

i + f(

Ni)

whe

re:

≤−

><−

≥−

=

dow

nwar

ds"

m

oves

he

ad"

and

if

dow

nwar

ds"

m

oves

he

ad"

and

if

upw

ards

"

mov

es

head

" an

d

if

upw

ards

"

mov

es

head

" an

d

if

)(

max

max

max

maxm

ax

NN

N

NN

NN

NN

NN

N

NN

NN

N

NN

Nf

ii

ii

ii

ii

i

Thi

s al

low

s to

rea

ch n

ewre

ques

ts a

s so

on a

s po

ssib

le.

8. M

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edia

File

Sys

tem


32 /

518.

4 D

isk

Sche

dulin

g / S

trat

egie

s

SCA

N: s

erve

s re

ques

t in

asce

ndin

g or

der

of tr

acks

, the

n in

des

cend

ing

orde

r,

then

in a

scen

ding

ord

er

C-S

CA

N: s

erve

s in

asc

endi

ng o

rder

onl

y (“

circ

ular

sca

n“)

ED

F (

Ear

liest

Dea

dlin

e F

irst)

0i

Nm

ax-1

SCA

N

C-S

CA

N

8. M

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edia

File

Sys

tem


33 /

518.

4 D

isk

Sche

dulin

g / S

trat

egie

s

SCA

N-E

DF:

1. g

roup

s re

ques

ts in

few

dea

dlin

es

(

in o

rder

to h

ave

man

y re

ques

ts f

or a

giv

en d

eadl

ine)

2. S

erve

s ac

cord

ing

to E

DF

(i.e

. sm

alle

st d

eadl

ine

firs

t) b

y us

ing

SCA

N o

r

C

-SC

AN

for

mem

bers

of

a gi

ven

dead

line

grou

p.

For

impl

enta

tion

: use

Dea

dlin

e pe

rtur

batio

n

Di ∈

N Í

Di´

= D

i + f(

Ni)

whe

re N i

= tr

ack

num

ber;

0 ≤ f(

Ni)

< 1

8. M

ultim

edia

File

Sys

tem


34 /

518.

4 D

isk

Sche

dulin

g / G

roup

Sw

eepi

ng S

ched

ulin

g (G

SS)

Req

uest

s ar

e se

rved

in c

ycle

s in

a r

ound

-rob

in m

anne

rIn

one

cyc

le r

eque

sts

divi

ded

into

gro

ups

Smoo

thin

g bu

ffer

may

be

need

ed (

to a

ssur

e co

ntin

uity

)

1.2

42

1.4

40

1.1

45

3.4

24

3.3

30

2.0

16

3.3

50

2.2

42

1.2

45

1.4

12

2.4

40

1.1

22

Cyc

le

Gro

up 1

SCA

N12

, 22,

45

(asc

endi

ng o

rder

)[i

n ne

xt c

ycle

: des

cend

ing

orde

r]42

, 40,

16

(des

cend

ing

orde

r)

1.2

42

1.4

40

1.1

45

Gro

up 2

SCA

N

1.2

42

1.4

40

1.1

45

Gro

up 3

SCA

N

Dea

dlin

e 1.

1

Dea

dlin

e 2.

0

24, 3

0, 5

0(a

scen

ding

ord

er) t

8. M

ultim

edia

File

Sys

tem


35 /

518.

4 D

isk

Sche

dulin

g / G

roup

Sw

eepi

ng S

ched

ulin

g (G

SS)

A p

artic

ular

str

eam

can

be

–th

e fir

st o

ne in

its

grou

p in

a g

iven

cyc

le

–an

d th

e la

st o

ne in

its

grou

p in

the

next

cyc

le

Thi

s ha

ppen

s if

the

scan

ord

er is

rev

erse

d, i.

e. if

we

have

an

odd

num

ber

of

grou

ps.

Thu

s w

e ne

e a

smoo

thin

g bu

ffer

in o

rder

to a

chie

ve c

ontin

uity

of

play

out.

8. M

ultim

edia

File

Sys

tem


36 /

518.

4 D

isk

Sche

dulin

g / G

roup

Sw

eepi

ng S

ched

ulin

g (G

SS)

- M

ixed

Str

ateg

y

Com

prom

ise

betw

een

–sh

orte

st s

eek

(“gr

eedy

“)

–ba

lanc

ed s

trat

egy

Dat

a re

trie

ved

from

dis

k ar

e pl

aced

in b

uffe

r; d

iffe

rent

que

ues

for

diff

eren

t

med

ia s

trea

ms

“Sho

rtes

t see

k“ s

erve

s th

e st

ream

who

se d

ata

bloc

k is

clo

sest

“Bal

ance

d“ s

erv

es th

e st

ream

whi

ch h

as th

e lo

wes

t util

izat

ion

of b

uffe

rs

(sin

ce th

is s

trea

m r

isks

to r

un o

ut o

f dat

a)

8. M

ultim

edia

File

Sys

tem


37 /

518.

4 D

isk

Sche

dulin

g / G

roup

Sw

eepi

ng S

ched

ulin

g (G

SS)

- M

ixed

Str

ateg

y

Filli

ng S

tatu

s of

Buf

fers

indi

cate

whe

n to

sw

itch

from

SS

TF

to “

Bal

ance

d“ a

nd

vice

ver

sa.

“Urg

ency

“ cr

iterio

n:

Ful

lnes

s i =

sm

all Í

Urg

en

cy =

hig

h

Í

Bal

ance

d st

rate

gy s

houl

d be

use

d

∑=

)

stre

ams

al

l(

Fu

llnes

s

1U

rgen

cy

ii

SST

F/B

alan

ced

cont

inuo

us s

trea

ms

8. M

ultim

edia

File

Sys

tem


38 /

518.

4 St

orag

e D

evic

es /

Dat

a St

ruct

urin

g

Con

tinuo

us d

ata

are

char

acte

rize

d by

con

secu

tive,

tim

e-de

pend

ent l

ogic

al d

ata

units

.

Bas

ic d

ata

unit:

Vid

eo -

fra

me

(sin

gle

vide

o im

age)

A

udio

- s

ampl

e (a

mpl

itude

of

the

anal

og a

udio

sig

nal)

The

des

ign

of d

ata

stru

ctur

e is

gui

ded

by tw

o re

quir

emen

ts:

–T

ime

cont

inuu

m o

f med

ia: M

edia

uni

ts c

onve

y th

eir

mea

ning

onl

y pr

esen

ted

cont

inuo

usly

–S

ynch

roni

zatio

n be

twee

n m

edia

: Tem

pora

lly c

oord

inat

ion

of d

iffer

ent m

edia

com

pone

nts

Con

tinui

ty R

equi

rem

ent Í

Def

ine

a co

ntin

uous

ly r

ecor

ded

sequ

ence

of

med

iaun

its (

vide

o, a

udio

or

both

) as

a S

tran

d. S

tran

ds m

ust b

epa

rtiti

oned

into

blo

cks

and

stor

ed o

n di

sk.

For

prov

idin

g di

rect

acc

ess

to a

ny o

f th

e m

edia

blo

cks

of th

e st

rand

a h

iera

rchi

cal i

ndex

stru

ctur

e is

use

d.

8. M

ultim

edia

File

Sys

tem


39 /

518.

4 St

orag

e D

evic

es /

Dat

a St

ruct

urin

g

Med

ia B

lock

s (M

B)

plac

ed a

ccor

ding

to th

e pl

acem

ent m

odel

Prim

ary

Blo

cks

(PB

) co

ntai

n a

sequ

ence

of

(MB

, dis

k-lo

catio

n) p

airs

Seco

ndar

y B

lock

s (S

B)

poin

ters

to P

B

Hea

der

Blo

ck (

HB

) ro

ot o

f th

e st

rand

(po

inte

rs to

all

SB, r

ecor

ding

leng

th, r

ate)

HB

MB

MB

PBM

BM

BPB

SB...

......

HB

SBSB

SB

SBSB

8. M

ultim

edia

File

Sys

tem


40 /

518.

4 St

orag

e D

evic

es /

Dat

a St

ruct

urin

g

Mul

tim

edia

Rop

e: a

ll m

edia

str

ands

whi

ch c

onst

itute

a lo

gica

l ent

ity

(e.g

. vid

eo a

nd a

ssoc

iate

d au

dio

of a

mov

ie)

ContinuityRequirement

Sync

hron

izat

ion

Req

uire

men

tA

udio

St

rand

1V

ideo

Stra

nd 1

Sync

hron

izat

ion

Req

uire

men

tA

udio

St

rand

2V

ideo

Stra

nd 2

8. M

ultim

edia

File

Sys

tem


41 /

518.

4 St

orag

e D

evic

es /

Dat

a St

ruct

ure

of a

mul

timed

ia r

ope

MultimediaRopeID

Creator

Length

PlayAccess

EditAccess

List of [

List of [

MediaStrandID

<StrandIntrvalStart,

StrandintervalEnd>

Media type

EncodingFormat

MediaRecordingRate

StorageGranularity

List of [ <MediaUnitID, RTS>

] MaximumAsynchrony

] List of [

RTSvalue

]]

Uni

que

IDId

entif

icat

ion

of th

e cr

eato

rL

engt

h of

the

rope

Lis

t of

user

or

grou

p ID

Uni

que

ID o

f m

edia

str

and

Stra

nd in

terv

al, i

n m

edia

uni

tsM

ediu

m o

f th

e st

rand

Stra

nd e

ncod

ing

form

at: M

PEG

, JPE

G, e

tc.

Rat

e of

rec

ordi

ng, i

n m

edia

uni

ts/s

Med

ia g

ranu

lari

ty, i

n m

edia

uni

ts/s

Med

ia u

nit a

nd is

t cor

resp

ondi

ng R

TS

Tol

erab

le a

sync

hron

y tr

esho

ld

Dis

cret

e sy

nchr

oniz

atio

n po

ints

Iden

titie

s of

syn

chro

niza

tion

poin

ts

Aud

ioV

ideo

8. M

ultim

edia

File

Sys

tem


42 /

518.

4 St

orag

e D

evic

es /

Dat

a St

ruct

ure

of a

mul

timed

ia r

ope

At t

he ti

me

of r

ecor

ding

tem

pora

l rel

atio

nshi

ps a

mon

g st

rand

s (m

ay b

e re

cord

ed

at d

iffe

rent

sit

es/t

imes

) w

ill b

e re

pres

ente

d by

RT

S =

Rel

ativ

e T

ime

Stam

p.

Dur

ing

play

back

all

med

ia u

nits

mus

t be

play

ed in

RT

S re

altio

n to

the

othe

r

stra

nds.

8. M

ultim

edia

File

Sys

tem


43 /

518.

4 St

orag

e D

evic

es /

Dat

a St

ruct

urin

g

Edi

ting

oper

atio

ns o

n ro

pes

man

ipul

ate

poin

ters

to s

tran

ds.

Inte

rval

s of

str

ands

can

be

shar

ed b

y di

ffer

ent r

opes

.St

rand

s ar

e no

t ref

eren

ced

by a

ny r

ope

can

be d

elet

ed, a

nd s

tora

geca

n be

rec

laim

ed.

Aud

io

Vid

eo

Rop

e1

Aud

io

Vid

eo

Rop

e1

Aud

io

Vid

eo

Rop

e2

Aud

io

Vid

eo

Rop

e2

INSE

RT

8. M

ultim

edia

File

Sys

tem


44 /

518.

4 St

orag

e D

evic

es /

Dat

a St

ruct

urin

g

Furt

her

oper

atio

ns:

–R

EC

OR

D [me

dia

][re

qu

est

ID, m

mR

pe

ID]

Rec

ords

a M

mro

pe r

epre

sent

ed b

y “mmRopeID

“ an

d co

nsis

ting

of s

ever

al

med

ia s

tran

ds u

ntil

a STOP

ope

artio

n is

issu

ed.

–P

LA

Y [m

mR

op

eID

, in

terv

al,

me

dia

] re

qu

est

ID

–S

TO

P [re

qu

est

ID]

8. M

ultim

edia

File

Sys

tem


45 /

518.

4 St

orag

e D

evic

es /

Dat

a St

ruct

urin

g

Ope

ratio

ns:

–IN

SE

RT

[ba

seR

op

e, po

sitio

n, m

edia

, w

ithR

op

e, w

ithIn

terv

al]

–R

EP

LA

CE

[b

ase

Ro

pe

, p

osi

tion

, m

ed

ia, w

ithR

ope

, w

ithIn

terv

al]

–S

UB

ST

RIN

G [b

ase

Ro

pe, m

ed

ia, in

terv

al]

–C

ON

CA

TE

[m

mR

ope

ID1

, m

mR

pe

ID2]

–D

EL

ET

E [ba

seR

op

e, m

edia

, in

terv

al]

Aud

io

Vid

eo

Rop

e1

Aud

io

Vid

eo

Rop

e1

Aud

io

Vid

eo

Rop

e2

Aud

io

Vid

eo

Rop

e2

RE

PLA

CE

8. M

ultim

edia

File

Sys

tem


46 /

518.

5 Sy

stem

Arc

hite

ctur

e

Mul

tim

edia

Sys

tem

mus

t coe

xist

wit

h th

e co

nven

tiona

l Non

Rea

l Tim

e

Env

iron

men

t (N

RT

E)

data

pro

cess

ing

Í M

any

oper

atin

g sy

stem

s pr

ovid

e ex

tens

ions

to s

uppo

rt m

ultim

edia

app

licat

ion

R

eal T

ime

Env

iron

men

t (R

TE

)

App

licat

ion

itse

lf n

ever

rea

lly to

uche

s th

e da

ta

Í ta

ke th

e sh

orte

st p

ossi

ble

path

fro

m s

ourc

e to

the

sink

8. M

ultim

edia

File

Sys

tem


47 /

518.

5 Sy

stem

Arc

hite

ctur

e

RT

E s

ched

uled

the

proc

esse

s ac

cord

ing

to

the

timin

g re

quir

emen

ts

Stre

am H

andl

ers

man

age

the

RT

E d

ata

flow

in a

ccor

danc

e w

ith th

e co

ntro

l ope

artio

ns o

f

the

NR

TE

App

licat

ions

acc

ess

stre

am h

andl

ers

by

esta

blis

hing

(cr

eatin

g) s

essi

ons.

(Exc

lusi

ve v

irtu

al s

trea

m h

andl

er to

use

for

the

appl

icat

ion)

App

licat

ion(

s)

Stre

am C

ontr

ol I

nter

face

(s)

even

tsco

ntro

l

NR

TE

deal

s w

ith a

ll da

ta th

at h

ave

no ti

min

g re

quir

emen

ts

RT

ESour

ceSt

ream

Han

dler

Stre

am H

andl

er

Sink

Stre

am M

anag

emen

t Sys

tem

(s)

8. M

ultim

edia

File

Sys

tem


48 /

518.

5 Sy

stem

Arc

hite

ctur

e / U

NIX

-bas

ed S

yste

ms

App

licat

ions

mak

e us

e of

sys

tem

s ca

lls in

the

NR

TE

Ext

ensi

ons

to th

e op

erat

ing

syst

em (

i.e. R

TE

)

are

part

of

the

kern

el s

pace

Cur

rent

impl

emen

tatio

ns:

SUN

OS

R

TE

doe

s no

t exi

st

AIX

RT

E e

xist

IRIX

on

Silic

on G

raph

ics

RT

E e

xist

Wor

ksta

tion

Ope

ratin

g Sy

stem

e.g.

Tra

ditio

nal

Sche

dule

r

e.g.

Dea

dlin

e

S

ched

uler

RT

E

NR

TE

App

licat

ions

user

sp

ace

kern

elsp

ace

8. M

ultim

edia

File

Sys

tem


49 /

518.

5 Sy

stem

Arc

hite

ctur

e / I

BM

OS/

2

OS/

2 M

ulti

med

ia P

rese

ntat

ion

Man

ager

/2

Med

ia D

evic

e M

anag

er

Med

ia C

ontr

ol I

nter

face

MC

I

Med

ia D

rive

r

Sour

ce H

WD

evic

eD

rive

r

Sour

ce

Stre

amH

andl

erSy

nc/S

trea

mM

anag

er

Stre

am M

anag

er H

elpe

rs

Stre

am D

ata

Buf

fers

Sink

Stre

amH

andl

er

Sink

HW

Dev

ice

Dri

ver

Rea

l Tim

eE

nvir

onm

ent (

RT

E)

Non

Rea

l Tim

e E

nvir

onm

ent (

NR

TE

)

Stre

am P

rogr

amm

ing

Inte

rfac

e SP

I

8. M

ultim

edia

File

Sys

tem


50 /

518.

5 Sy

stem

Arc

hite

ctur

e / I

BM

OS/

2

Mul

tim

edia

Pre

sent

atio

n M

anag

er/2

(M

MPM

/2)

–P

art o

f IB

M´s

Ope

artin

g S

yste

m/2

(O

S/2

)

–W

ell-s

uite

d fo

r m

ultim

edia

sup

port

ing

pree

mpt

ive

mul

titas

king

, prio

rity

sche

dulin

g, d

eman

d-pa

ged

virt

ual m

emor

y st

orag

e, e

tc.

Med

ia C

ontr

ol I

nter

face

(M

CI)

(de

vice

inde

pend

ent p

rogr

amm

ing

inte

rfac

e)–

Ope

n, c

lose

, sta

tus

of d

evic

e (f

or a

ll de

vice

s)

–P

lay,

rec

ord,

res

ume,

sto

p (p

layb

ack,

rec

ord)

–S

et c

ue p

oint

(al

low

s fo

r sy

nchr

onia

tion)

–G

et ta

ble

of c

onte

nts

of a

CD

-RO

M (

devi

ce-s

peci

fic c

omm

and)

8. M

ultim

edia

File

Sys

tem


51 /

518.

5 Sy

stem

Arc

hite

ctur

e / I

BM

OS/

2

Stre

am P

rogr

amm

ing

Inte

rfac

e (S

PI)

–Im

plem

enta

tion

of d

ata

stre

amin

g an

d sy

nchr

oniz

atio

n

–A

cces

s to

the

Syn

cStr

eam

Man

ager

(co

ordi

nate

s an

d m

anag

es th

e bu

ffers

,

sync

hron

.)

Eas

e of

use

sev

eral

leve

ls

–S

tyle

gui

de fo

r ap

plic

atio

ns

–U

nifie

d gr

aphi

cal i

nter

face

s

–A

pplic

atio

n de

velo

pers

and

dev

ice

prov

ider

s ca

n in

terg

rate

thei

r ow

n I/O

proc

esse

s, s

trea

m h

andl

ers,

etc

.

Documents

8. Multimedia File Systems