Efficient Locally Trackable from seed Deduplication in Replicated - - PowerPoint PPT Presentation

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Efficient Locally Trackable from seed Deduplication in Replicated - - PowerPoint PPT Presentation

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technology Efficient Locally Trackable from seed Deduplication in Replicated Systems Joo Barreto and Paulo Ferreira Distributed Systems Group INESC-ID/Technical University Lisbon, Portugal www.gsd.inesc-id.pt Instituto de Engenharia de

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Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa

technology

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Efficient Locally Trackable Deduplication in Replicated Systems

João Barreto and Paulo Ferreira Distributed Systems Group INESC-ID/Technical University Lisbon, Portugal

www.gsd.inesc-id.pt

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Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa

technology

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Bandwidth remains scarce

02/12/2009 Middleware 2009

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Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa

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Collaboration through data replication

02/12/2009 Middleware 2009

Site S Site R

File A, v4 File A, v3 File A, v2 File B, v4 File B, v3 File C, v8 File C, v7 File A, v3 File A, v2 File B, v3 File C, v8 File C, v9

Distributed users share objects A, B and C At each m om ent: S stores versions( S) and R stores versions( R)

versions( S) versions( R)

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Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa

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The bottleneck: synchronization

02/12/2009 Middleware 2009

Site S Site R

File A, v4 File A, v3 File A, v2 File B, v4 File B, v3 File C, v8 File C, v7 File A, v3 File A, v2 File B, v3 File C, v8 File C, v9

1 . Determ ine w hich versions to transfer

versions( S) versions( R)

Synchronize to

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Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa

technology

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The bottleneck: synchronization

02/12/2009 Middleware 2009

Site S Site R

2 . Transfer versions

versions( S) versions( R)

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Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa

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Deduplication: exploiting redundancy

02/12/2009 Middleware 2009

Site S Site R

versions( S)

+ References to chunks in versions( R)

versions( R)

How to determine which chunks are redundant?

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Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa

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Locally trackable vs untrackable redundancy

02/12/2009 Middleware 2009

Site S Site R

versions( S) versions( R)

Locally Trackable Redundancy

chunk to transfer exists in some version that is both in versions(S) and versions(R)

Locally Untrackable Redundancy

  • therwise
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Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa

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Existing approaches: compare-by-hash

02/12/2009 Middleware 2009

Site S Site R

versions( S) versions( R)

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Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa

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Existing approaches: advantages and shortcomings Compare-by-hash  Detects both locally trackable and untrackable redundancy  Detects redundancy across any versions and/or objects Additional round-trip Limited precision:

– smaller chunks may not compensate hash-exchange and hash-lookup overheads

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Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa

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Existing approaches: delta encoding

02/12/2009 Middleware 2009

Site S Site R

versions( S) versions( R)

Calculate deltas from most recent versions versions(R) to each version to transfer. Using local, high-precision algorithm s.

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Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa

technology

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Existing approaches: advantages and shortcomings Compare-by-hash  Detects both locally trackable and untrackable redundancy  Detects redundancy across any versions and/or objects Additional round-trip Limited precision:

– smaller chunks may not compensate hash-exchange and hash-lookup overheads

Delta Encoding Only detects locally trackable redundancy Limited to pairs of versions  High-precision local redundancy detection  Redundancy detection can

  • ccur ahead of transfer

time  Simple protocol Can we devise a solution that borrows the advantages from both approaches?

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Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa

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  • 3. For each chunk to transfer, if the chunk is also in some

version in C, simply send a reference to that version

  • 2. Determine C = versions(S) ∩ versions(R)

Our contribution: redFS Site S Site R

versions( S) versions( R)

  • 0. Use local high-precision compare-by-hash

algorithm to pre-compute local redundancy relations

[ S:5 ] [ S:4 ] [ R:4 ] [ R:5 ] [ S:3 ] [ S:5 ] [ S:4 ] [ S:6 ] [ R:4 ] [ S:3 ] [ S:6 ] [ R:3 ]

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Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa

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What does redFS achieve? Compare-by-hash  Detects both locally trackable and untrackable redundancy  Detects redundancy across any versions and/or objects Additional round-trip Limited precision:

– smaller chunks may not compensate hash-exchange and hash-lookup overheads

Delta Encoding Only detects locally trackable redundancy Limited to pairs of versions  High-precision local redundancy detection  Redundancy detection can

  • ccur ahead of transfer

time  Simple protocol

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Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa

technology

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Compare-by-hash  Detects both locally trackable and untrackable redundancy  Detects redundancy across any versions and/or objects Additional round-trip Limited precision:

– smaller chunks may not compensate hash-exchange and hash-lookup overheads

Delta Encoding Only detects locally trackable redundancy Limited to pairs of versions  High-precision local redundancy detection  Redundancy detection can

  • ccur ahead of transfer

time  Simple protocol What does redFS achieve?

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Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa

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What does redFS achieve?

02/12/2009 Middleware 2009

Simpler protocol, Able to detect finer-grained redundancy Locally trackable redundancy across pairs of consecutive versions of sam e

  • bject

Delta Encoding Detectable forms of redudancy Com pare-by- hash

redFS

Any redundancy Any locally trackable redundancy ≈ More complicated protocol, Limited precision

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Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa

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Evaluation: methodology

  • We evaluated different solutions from every approach:

– RedFS full implementation – LBFS, rsync, TAPER (compare-by-hash) – xdelta, svn (delta encoding)

  • Two distributed sites, network with different bandwidths

(3Mbps to 100Mbps)

  • Real workloads

– Single-writer Scenarios – Multi-writer Scenarios

02/12/2009 Middleware 2009

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Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa

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Evaluation: single-writer multi-reader scenarios

02/12/2009 Middleware 2009

Site S ( W riter) Site R ( Reader) v0 of a set of files

(e.g. gcc 3.3.1 source code)

v0 of a set of files

(e.g. gcc 3.3.1 source code)

v1 of a set of files

(e.g. gcc 3.4.1 source code)

deduplication

v1 of a set of files

(e.g. gcc 3.4.1 source code)

Sam e m ethodology and w orkloads as in recent com pare-by-hash papers ( e.g. LBFS [ SOSP’0 1 ] , TAPER [ FAST’0 5 ] ) All redundancy is locally trackable!

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Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa

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Evaluation: transferred volumes in single-writer multi-reader scenarios

(Except for particularly suited workloads such as this one) RedFS transfers less than delta-encoding RedFS transfers less (or, in few exceptions, comparable) bytes than all compare-by-hash solutions

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Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa

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Best performance with low bandwidth (due to high deduplication efficiency) Best performance with high bandwidth (due to protocol simplicity)

Evaluation: performace in single-writer multi-reader scenarios

redFS LBFS Plain svn (delta encoding) rsync

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Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa

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Evaluation: multi-writer scenario

02/12/2009 Middleware 2009

Site S ( W riter) Site R ( W riter) v0 of working set v0 of working set vS of working set

deduplication

vR of working set

W orkloads from collaborative activity betw een groups of teachers and students during 1 -sem ester courses. Locally untrackable redundancy can now occur!

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Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa

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Evaluation: multi-writer scenario

Q: How much locally untrackable redundancy? A: Only 1% to 4% of all redundancy generated over +3 months was locally untrackable

02/12/2009 Middleware 2009

Advantages of redFS persist even in real scenarios where locally untrackable redundancy can occur (both in transferred volume and performance)

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Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa

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Conclusions

  • Compare-by-hash trades simplicity and efficiency for the

ability to detect any redundancy

  • In relevant scenarios, most redundancy is locally trackable

– Including the same scenarios that most compare-by-hash papers use to motivate their works

  • By exclusively detecting locally trackable redundancy we

can outperform compare-by-hash

– One forgotten example: Delta Encoding

  • Our contribution: RedFS’s algorithm

– Fully implemented as open source distributed file system – Evaluation shows it outperforms both compare-by-hash and delta encoding

12/2/2009

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Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa

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Thank you.

Questions?

www.gsd.inesc-id.pt/~jpbarreto

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Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa

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Ok, but at which storage cost?

Plain storage Deduplicated storage (128-byte chunks) Deduplicated storage (2KB chunks) Deduplicated storage (8KB chunks)