Distributed DBMS reliability Distributed DBMS reliability - - PowerPoint PPT Presentation

Distributed DBMS reliability Distributed DBMS reliability

• ! "# $% &#

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• !(*(*+((,

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Outline (distributed DB)

• 2 '( ⋆

⋆

• '( . ⋆
• 34% '( 5 ⋆
• ! '( ⋆

2'( ⋆

• ! "# $% &#

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⋆

➡ 2'( ⋆ ➡ '4' '( ⋆ ➡ ⋆

⋆ Özsu and Valduriez, (3rd Ed.), 2011

Outline (today)

• 64'( ⋆

➡ 24 ➡ 24 ➡ 4

✦ !+(%'

• ! "# $% &#

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⋆ Özsu and Valduriez, (3rd Ed.), 2011

Reliability

%0

7+ 4 4

• ! "# $% &#

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• '( )8

Fundamental Definitions

• 64

➡ 9+(+((4(* ➡ 9+(+((4(*

(*

• 9*4

➡ !(((4

• :

➡ !(*4((*(

• ! "# $% &#

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Types of Failures

• !

➡ !4, ➡ !4,

• 4

➡ :-4-+4-< ➡ 4-4 ➡ %*

➡ :4*((( ➡ 7()=

• ! "# $% &#

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➡ %4--4> (,

• '

➡ ?)* ➡ @+,

Update Strategies

• 2

➡ /((*( ➡ -

• A

➡ /((+*4

(*

• ! "# $% &#

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(*

➡ ?-4

In*Place Update Recovery Information

?

/*44(- /*44(- + 4

@+

• C

A A

• ! "# $% &#

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• ?

Logging

!(4(*4( 44 !(4 44 !(4

➡ ➡ 4 ➡ 4(( ➡ * ➡ +*

• ! "# $% &#

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<

Why Logging?

C*40

➡ D((6/A4 ➡ D((6/A4

• ➡ D((C@A4

4 (

• /
• ! "# $% &#

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• /

REDO Protocol

6/A A

• @+
• 6/AD
• ?

6/A

• ! "# $% &#

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• 6/AD
• !(6/A(
• 6/A+(+4

4-4

➡ 44,44

UNDO Protocol

@+ A

• @+
• ?

C@A A

• ! "# $% &#

'( )

• C@AD (E
• !(C@A(
• C@A+(4-

4(

➡ 4-,44

When to Write Log Records Into Stable Store

9

• :
• :

➡ 4+ ➡ 4( ➡ F!/:92?C6/A''C6G

H*4 4(

• C

➡ 4+ ➡ F!/:92?C6/A''C6G

• ! "# $% &#

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F!/:92?C6/A''C6G

H*(( (*

• 0H9(? H9?

Write–Ahead Log Protocol

• @0

➡ 24(-(( ➡ 24(-((

A4( (

➡ A-((*

@( (

• H9?0
• (((

+(

• ! "# $% &#

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H(-((+

((

Execution of Commands

'0

I

• +
• 21

4?6

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• *

Execution Strategies

➡ '(+(4

+?6= +?6=

✦ 1)1

➡ (?6(+

(D1=

✦ ()(

• %10
• ! "# $% &#

'( )5

• %10

➡ 1)( ➡ 1)( ➡ 1)( ➡ 1)(

No*Fix/No*Flush

• 9

➡ 4(*+( ➡ 4(*+(

4-,

➡ ?6

• '

➡ ?6+JIIK( ➡ 4+,

• 6*
• ! "# $% &#

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• 6*

➡ :(((*(JIK

JIIK(- 4?6

➡ :((4(*JIK(-

14?6

No*Fix/Flush

• 9

➡ 4(*+( ➡ 4(*+(

4-,

➡ ?6

• '

➡ ?6 (

✦ -,

➡ ?6+JIIK(

• ! "# $% &#

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➡ ?6+JIIK(

• 6*

➡ @ ➡ %

Fix/No*Flush

• 9

➡ @((*+ ➡ @((*+ ➡ 6(

• '

➡ ?6+JIIK( ➡ 4+, ➡ ?6 ((+

*4

• ! "# $% &#

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*4

• 6*

➡ % ➡ @

Fix/Flush

• 9

➡ @((*+ ➡ @((*+ ➡ 6(

• '(+(*4

➡ ?6 (

✦ -,

➡ ?6 ((+

*4

• ! "# $% &#

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*4

➡ ?6+JIIK(

• 6*

➡ @4(

Checkpoints

• (,(

+( +(

➡ 9*(+(

• 9(,4(
• (,0

HI(, ( '((,(

• ((+-4*
• ! "# $% &#

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• ((+-4*
• HI(, (

Media Failures – Full Architecture

4 4

• 6

H H 6 4

• :(-

:(

• ! "# $% &#

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9(*

• 9(*
• H

H

Distributed Reliability Protocols

• '

➡ 7+1 ➡ 7+1 ➡ 20(+44=

• !

➡ 2-(+((* ➡ ! 0(((+

((

• 6*4

➡ H(-(+(+(((*

• ! "# $% &#

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➡ H(-(+(+(((*

(4,

➡ " 0(+(

(*

• 2*4 ⇒ ,

Two*Phase Commit (2PC)

# 0!((4 (4 (4 $ 0!() L-((-+,L

➡ 0!((+((

+(((1

➡ !" 0!((((1(

• M'60
• ! "# $% &#

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M'60

• !(4

*

• /N*40!(4(

*

2PC Protocol Actions

% '

#$#%#& #$#%#& @ ' %&'!(&" F )*&+*!+&, @ (

• (
• )&#%
• **+

&$+ (

• (

,**

• &'
• ! "# $% &#

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@ (

• 9

' +(- +(- (**

• %"

* (**

• &.%

.#% .#% &.% ( ,,

• C

Centralized 2PC

! !

• !

! ! ! ! ! ! !

• ! "# $% &#

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• *)

* )

• )

%( %(

Linear 2PC

%( % &')&9 %( M')M9 &')&9 &')&9 &')&9

• .

8 ; @ M')M9 M')M9 M')M9 M')M9

≈ ≈

• ! "# $% &#

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%( &'0&'-&90&9-M'0M-M90M

Distributed 2PC

' % %

• ! "# $% &#

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• *)

* )

• 4

%( %(

Variations of 2PC

• %%'%'
• '4(4
• '4(4
• ➡ 6
• ! "# $% &#

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State Transitions in 2PC

#$#%#& )&#% ' % & #$#%#&

• &'

% & M % & M &

• ! "# $% &#

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& M M 9, M 9,

' %

& M &.% .#% .#% &.%

Site Failures * 2PC Termination

• !H92!

➡ '4

'AA62@9!A6

➡ '4 ➡ '4

• !9A6!'A2!

➡ 4,+(, ➡ 64JK

JK*

• #$#%#&

)&#%

' %

• ! "# $% &#

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& M

&.% .#%

& M

Site Failures * 2PC Termination

• !2@2!29?

➡ '(*

2@2!29?

%96!2'2%9@!

2@2!29?

➡ C4

• !6/9F

➡ 4,

➡ 64J*K

• 2-(4

#$#%#&

• &'

% &

M

% & M

• ! "# $% &#

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• 2-(4

*, 9 6/9F,.

➡ . 2@2!29?0. ➡ . 6/9F0( ➡ . 9A6!)'A2!0. J*

K)K*

M

9, M 9,

&.% .#%

Re*election of the coordinator

• 2<
• <(,+(((4
• <(,+(((4
• (((

➡ /444*

• +,( 20

➡ %* ➡ %4 ➡ %(

• ! "# $% &#

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➡ %( ➡ 9+1((((

(

• %',

Site Failures * 2PC Recovery

• :2@2!29?

➡ (*4

'AA62@9!A6

➡ (*4

• :H92!

➡ 6(*4

• :9A6!)'A2!

➡ @((, (*

*

➡ A(+*,(

#$#%#& )&#%

' %

&

&

• ! "# $% &#

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➡ A(+*,(

9A6!)'A2!

& M

&.% .#%

& M

Site Failures * 2PC Recovery

• :2@2!29?

➡ C4*4

%96!2'2%9@!

➡ C4*4

• :6/9F

➡ !((

(

➡ !6/9F

*,(

• :9A6!'A2!

#$#%#&

• &'

% & % &

• ! "# $% &#

'( ).;

• :9A6!'A2!

➡ @(

M

9, M 9,

&.% .#%

2PC Recovery Protocols – Additional Cases

94

• '+JIK
• '+JIK

JK

➡ H92!O*,*4H92!

JK

• %+J4KJ*

K

➡ 6/9F ➡ *,*46/9F

• ! "# $% &#

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➡ *,*46/9F

• %+JKJ*

K

➡ 4(*4

2PC Recovery Protocols – Additional Cases (cont’d)

• '

( (

➡ 'A2!9A6! ➡ (6/9F

• %+JKJK

,+

➡ 'A2!9A6! ➡ +(4'A2!9A6!

• ! "# $% &#

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➡ +(4'A2!9A6!

Problem With 2PC

• ,

➡ 64((+( ➡ 64((+( ➡ 2-,*4 ➡ ,*4

• 2*4
• 7+*-,+(0

➡ 2*414O

*41+((

• ! "# $% &#

'( ).

*41+((

• .%',
• '+,

➡ @,1

More Problematic Failure Types

• H4

➡ 9*-* ➡ 9*-*

• /

➡ 24+,10 ➡ (*0( ➡ 90

• ! "# $% &#

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