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Disk Backup Through Algebraic Signatures For A Scalable Distributed Data Structure in SDDS-2002 System. Witold Litwin [email protected] Riad Mokadem Riad.Mokadem @dauphine.fr Thomas Schwartz [email protected]. Plan. Introduction The SDDS-2002 Backup Scheme - PowerPoint PPT Presentation
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Witold Litwin [email protected]
Riad Mokadem [email protected]
Thomas Schwartz [email protected]
Disk Backup Through Algebraic Disk Backup Through Algebraic SignaturesSignatures
For ForA Scalable Distributed Data A Scalable Distributed Data
StructureStructurein SDDS-2002 Systemin SDDS-2002 System
2
PlanPlan
IntroductionIntroduction
The SDDS-2002 Backup SchemeThe SDDS-2002 Backup Scheme
Experimental performance analysis.Experimental performance analysis.
Conclusion.Conclusion.
3
IntroductionIntroduction
Need for RAM SDDS storage to the disk File Backup
Failure of a server
File Eviction Sharing of RAM
Among different SDDS files With other apps
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IntroductionIntroduction
Write to the disk only the parts (pages) changed since last backup “Dirty bit” approach inapplicable Page signature calculus: a possibility provided that:
Fast Precise Scalable
Shorter signatures may become longer without total recalculus
Not the case of SHA-1 nor of any other previous proposed schema
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The SDDS-2002 Backup SchemeThe SDDS-2002 Backup Scheme File BackupFile Backup
Client
…… … …Server RAM Buckets
Server Disks
Store command Multicast)
Distributed Distributed StoringStoring
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The SDDS-2002 Backup SchemeThe SDDS-2002 Backup Scheme File LoadFile Load
Client
…… …
Load command Multicast)
Server RAM Buckets
Server Disks
Distributed Distributed LodingLoding
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Internal Organization of Bucket in Internal Organization of Bucket in SDDSSDDS
En-tête
Index SDDS B+-tree
Pages de donnéesData FileData File
Index : a few Kbytes up to MByteIndex : a few Kbytes up to MByte
Data file : Dozens of Mbytes up to GBytes Data file : Dozens of Mbytes up to GBytes
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Page GranularityPage Granularity Carefull choice
Smaller page More individual writes if many random updates Less data transferred if a few updades
Larger pages Vice versa
Optimal size ? Good question
Our choice 16 KB for data
Although 64 KB pages proved best for data page signature calculus speed
256 B for index
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Page SignaturePage Signature Algebraic SignaturesAlgebraic Signatures
• Galois Field GF (Galois Field GF (216) )
• Log / Antilog multiplicationLog / Antilog multiplication
• Page Page P P has 2-byte symbols has 2-byte symbols pp11 , p , p22, ….p, ….p
nn
• The signature formula is : The signature formula is :
• for each for each p’i = antilog p’i
•for each for each = : = : , 2, 3…
Sign ( P )= p’i i i = 1..n
Sign (P)= (Sign ( P ), Sign 2( P ),…Sign m( P ))
We put m = 2 to SDDS-2002
i=1,2...ni=1,2...n
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Experimental Performance AnalysisExperimental Performance AnalysisHardware ConfigurationHardware Configuration
1.8 GHz P4 Servers1.8 GHz P4 Servers 800 MHz P3 Client 800 MHz P3 Client 500 MHz P3 Name Server500 MHz P3 Name Server 1 Gbs Ethernet1 Gbs Ethernet Windows 2000 Server OSWindows 2000 Server OS
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Experimental Performance Experimental Performance SDDS-2002SDDS-2002
Initial File Store Time (No Signature Calculus)Initial File Store Time (No Signature Calculus)
11 2 3 4 2 3 4 File serversFile servers
Time Time
(Sec)(Sec)
120120
100100
8080
6060
4040
2020
File Size: 393MOFile Size: 393MO
25 000 Records25 000 Records
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Initial File Store TimeInitial File Store Time(Time Series) (Time Series)
0
20000
40000
60000
80000
100000
120000
140000
100 150 1000 10000 25000
One Serv
Tw o Serv
Tree Serv
Number of Number of recordrecord
Storage Storage Time Time
(Ms)(Ms)
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FileFile Load TimeLoad Time
120120
100100
8080
6060
4040
2020
11 2 3 4 2 3 4
(Sec)(Sec)
# of servers# of servers
File Size :File Size :
393MO393MO
Practically the same as the 1Practically the same as the 1stst backup time backup time
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File Storage Performance AnalysisFile Storage Performance Analysis
Bucket
size (MB)
Number of
record
Signature
calculus (ms)
Signature
Calculus
per/MB
(ms)
Totalstore time (ms)
Store time
for 0 % change
(ms)
Gain (%)
Store time for 5 %
change
(ms)
Gain(%)
1.88 100 46 24.46 562 50 91.1 65 88.43
2.7 150 78 28.8 781 82 89.51 95 87.83
17.6 1000 438 24.88 5078 438 91.38 453 91.07
158 10000 4068 25.74 46406 4071 91.23 4085 91.19
393 25000 11003 27.9 117859
11003 91.33 11018 90.65
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SHA-1 / Algebraic SignaturesSHA-1 / Algebraic SignaturesBucket
size(Mb)
Number of
record
Algebraic
signature
calculus (ms)
SHA-1
calculus (ms)
Initial Store time with
SHA-1(ms)
Initial Store time with alg. sign.(ms)
SHA-1
Store time for 5 %
change
(ms)
Alg. sign
Store time for 5 %
change
(ms)
Gain
(%)
1.88 100 46 70 602 562 85 65 30
2.7 150 78 103 799 781 119 95 25
17.6 1000 438 680 5278 5078 697 453 53
158 10000 4068 6088 47906 46406
6102 4085 49
393 25000 11003 15403
119342 117859
15418
11018
40
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Algebraic / SHA-1 Signature Calculus TimeAlgebraic / SHA-1 Signature Calculus Time
02000400060008000
1000012000140001600018000
0 2 4 6
Bucket Size (MB)
Algebraic signature
Cryptographicsignature
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ImplImpleementation in SDDS 2002mentation in SDDS 2002Interactive Client InterfaceInteractive Client Interface
User User interfaceinterface
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ImplImpleementation in SDDS 2002mentation in SDDS 2002Execution Listing at the ServerExecution Listing at the Server
}}
1st Request for storage : 1st Request for storage : New File New File Signature Calculus (375 ms) Signature Calculus (375 ms) Disk write of all pages (4922 ms) Disk write of all pages (4922 ms)
2nd Request for storage : 2nd Request for storage : No changes found (375 ms) No changes found (375 ms)
3rd Request for storage : 3rd Request for storage : 1 page changed 1 page changed (375 + 16 ms) (375 + 16 ms)
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ConclusionConclusion• The algebraic signature based file backup worksThe algebraic signature based file backup works
• Present in SDDS-2002 prototypePresent in SDDS-2002 prototype
• Offers advantages over the traditional approachOffers advantages over the traditional approach
• No change to existing codeNo change to existing code
• No run-time overheadNo run-time overhead
• Future workFuture work
• SignaturesSignatures
•Calculus, Alg. Properties, Apps…Calculus, Alg. Properties, Apps…
• Automatic SDDS File eviction Automatic SDDS File eviction
Thank You Thank You forfor
Your AttentionYour Attention