SIAS-Chains: Snapshot Isolation Append Storage Chains. Dr. Robert Gottstein Prof. Ilia Petrov M.Sc. Sergej Hardock Prof. Alejandro Buchmann

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1 SIAS-Chains: Snapshot Isolation Append Storage Chains Dr. Robert Gottstein Prof. Ilia Petrov M.Sc. Sergej Hardock Prof. Alejandro Buchmann

2 Motivation: Storage Technology Evolution Significant impact of storage technology evolution Random Throughput [IOPS] read write Sequential Throughput [MB/s] KB 16KB 32KB 64KB 128KB 256KB 512KB 1024KB Blocksize [KB] Blocksize [KB] Intel X25-E SLC SSD Seq. Read/Write: 250 / 170 MB/s Read/Write IOPS (4K): / Latency Read/Write (4K): 0.075/0.085 ms Erase before overwrite slow & large granularity Savvio 15k HDD Seq. Read / Write: 160 MB/s Read/Write IOPS: 350 / 300 Latency Read/Write: 3.2 / 3.5 ms Direct overwrite

Random Throughput [IOPS] Motivation: Storage Technology Evolution Significant impact of storage technology evolution 30000 3000 300 30 4 8 16 32 64 128 256 Blocksize [KB] Blocksize [KB] DBMS needs to

3 Random Throughput [IOPS] Motivation: Storage Technology Evolution Significant impact of storage technology evolution Blocksize [KB] Blocksize [KB] DBMS needs to Leverage: Fast Reads Intel X25-E SLC SSD Savvio 15k HDD Low Latencies Seq. Read/Write: 250 Asymmetry / 170 MB/s Seq. Read / Write: 160 MB/s Read/Write IOPS (4K): 35 Parallelism 000 / Read/Write IOPS: 350 / 300 Latency Read/Write (4K): 0.075/0.085 Write Sequentialization ms Latency Read/Write: 3.2 / 3.5 ms Erase before overwrite Direct overwrite slow & large granularity read write Sequential Throughput [MB/s] HDD: symmetric read/write; high Latency; big block; rotational moving parts SSD: asymmetric read/write; low Latency; No In-Place Updates; small block; write sequentialization; Intrinsic Parallelism; Endurance 8KB 16KB 32KB 64KB 128KB 256KB 512KB 1024KB

4 Random Throughput [IOPS] Motivation: Storage Technology Evolution Significant impact of storage technology evolution Blocksize [KB] Blocksize [KB] DBMS needs to Leverage: Fast Reads Intel Multi X25-E Version SLC SSD DBMS: Savvio 15k HDD Low In principle Latenciessuitable for asymmetric storage. Seq. Read/Write: Parallelism. Out-of 250 Asymmetry / 170 place MB/s updates. Seq. Sequentialization... Read / Write: 160 MB/s Read/Write IOPS (4K): 35 Parallelism 000 / Read/Write IOPS: 350 / 300 Latency Read/Write (4K): 0.075/0.085 Write Sequentialization ms Latency Read/Write: 3.2 / 3.5 ms Erase before overwrite Direct overwrite slow & large granularity read write Sequential Throughput [MB/s] HDD: symmetric read/write; high Latency; big block; rotational moving parts SSD: asymmetric read/write; low Latency; No In-Place Updates; small block; write sequentialization; Intrinsic Parallelism; Endurance 8KB 16KB 32KB 64KB 128KB 256KB 512KB 1024KB

5 Introduction Version Organization & Invalidation Relation R A. W 1 [X 0 =9];C 1 ; W 2 [X 1 =10];C 2 ; W 3 [X 2 =11];C 3 ; Item X Version X 0 Version X 1 Version X Tuple X 0 Value=9 (ts create =123, ts inval =null) =134) Visibility Timestamps creation: ts create invalidation: ts inval Tuple X 1 Value=10 (ts create =134, ts inval =null) =141) Tuple X 2 Value=11 (ts create =141, ts inval =null) Asymmetric: Fast Reads & Slow Writes Low Latency: no moving parts No In-Place Updates: Need to erase first (slow) Intrinsic Parallelism: Read in parallel

6 Introduction Version Organization & Invalidation Relation R A. W 1 [X 0 =9];C 1 ; W 2 [X 1 =10];C 2 ; W 3 [X 2 =11];C 3 ; Item X Version X 0 Version X 1 Version X Tuple X 0 Value=9 (ts create =123, ts inval =null) =134) Visibility Timestamps creation: ts create invalidation: ts inval Tuple X 1 Value=10 (ts create =134, ts inval =null) =141) Tuple X 2 Value=11 (ts create =141, ts inval =null) Asymmetric: Fast Reads & Slow Writes Low Latency: no moving parts No In-Place Updates: Need to erase first (slow) Intrinsic Parallelism: Read in parallel Version Organization & Invalidation Small Random Updates

7 SIAS: Snapshot Isolation Append Storage SIAS in a nutshell: redesign architecture and algorithms W 1 [X 0 =9];C 1 ; W 2 [X 1 =10];C 2 ; W 3 [X 2 =11];C 3 ; Version Organization Backward Chaining of versions Chain identified by virtual ID (VID) Store the entrypoint in datastructure: VID map Tuple Tuple X Value=9 0 Value=9 (ts (ts create =123, ts inval =null) create =123, ts inval =134) Tuple Tuple X Value=10 1 Value=10 (ts (ts create =134, ts inval =null) create =134, ts inval =141) Tuple X 2 Value=11 (ts create =141, ts inval =null) New Invalidation Invalidation coded within the chain One-place Invalidation Append Storage Append tuple versions to a new page Write page when filled or on a threshold Tuple X 2 Value=11 (ts create =141, VID=34) Tuple X 1 Value=10 (ts create =134, VID=34) Tuple X 0 Value=9 (ts create =123, VID=34) Item X VID=34

8 SIAS: Snapshot Isolation Append Storage SIAS in a nutshell: redesign architecture and algorithms W 1 [X 0 =9];C 1 ; W 2 [X 1 =10];C 2 ; W 3 [X 2 =11];C 3 ; Version Organization Backward Chaining of versions Chain identified by virtual ID (VID) Store the entrypoint in datastructure: VID map Tuple Tuple X Value=9 0 Value=9 (ts (ts create =123, ts inval =null) create =123, ts inval =134) Tuple Tuple X Value=10 1 Value=10 (ts (ts create =134, ts inval =null) create =134, ts inval =141) Tuple X 2 Value=11 (ts create =141, ts inval =null) New Invalidation Invalidation coded within the chain One-place Invalidation Variant above is widely spread in multi version databases! Append Variant Storage below allows to address Flash storage properties Append tuple versions to a new page Write page when filled or on a threshold Tuple X 2 Value=11 (ts create =141, VID=34) Tuple X 1 Value=10 (ts create =134, VID=34) Tuple X 0 Value=9 (ts create =123, VID=34) Item X VID=34

9 Multi Version DBMS Example W 1 [X 0 =9];C 1 ; W 2 [X 1 =10];C 2 ; W 3 [X 2 =11];C 3 ; Invalidation X 0 =9 X 1 =10 X 2 =11 Item X Creation Ti Transaction T1 T2 T3 P n DB Page P 0 P 10 P 21 P 32 P 4 P... B n Device Block B 0 B 10 B 21 B 32 B 4 B...

10 Multi Version DBMS Example W 1 [X 0 =9];C 1 ; W 2 [X 1 =10];C 2 ; W 3 [X 2 =11];C 3 ; Invalidation X 0 =9 X 1 =10 X 2 =11 Item X Creation Ti Transaction T1 T2 T3 P n DB Page P 0 P 10 P 21 P 32 P 4 P... B n Device Block B 0 B 10 B 21 B 32 B 4 B...

11 Multi Version DBMS Example W 1 [X 0 =9];C 1 ; W 2 [X 1 =10];C 2 ; W 3 [X 2 =11];C 3 ; Invalidation X 0 =9 X 1 =10 X 2 =11 Item X Creation T1 T2 P 0 P 10 P 21 P 32 P 4 P... Random T3 Writes In-Place Updates Mixed Load Ti P n B n Transaction DB Page Device Block B 0 B 10 B 21 B 32 B 4 B...

12 SIAS Principle Example Tuple Append Storage Management W 1 [X 0 =9];C 1 ; W 2 [X 1 =10];C 2 ; W 3 [X 2 =11];C 3 ; Invalidation X 0 =9 X 1 =10 X 2 =11 Item X Creation T1 T2 T3 VID Map Ti P n Transaction DB Page P n X 01 2 B n Device Block B k-3 B k-2 B k-1 B k Write Order No in-place invalidation Append versions instead of pages Write filled pages DBMS specific Write reduction Simplyfied Buffer Management

13 SIAS Principle Example Tuple Append Storage Management W 1 [X 0 =9];C 1 ; W 2 [X 1 =10];C 2 ; W 3 [X 2 =11];C 3 ; Invalidation X 0 =9 X 1 =10 X 2 =11 Item X Creation T1 T2 T3 VID Map Ti P n Transaction DB Page P n X 01 2 B n Device Block B k-3 B k-2 B k-1 B k Write Order No in-place invalidation Append versions instead of pages Write filled pages DBMS specific Write reduction Simplyfied Buffer Management

Block B k-3 B k-2 B k-1 B k Write Order No in-place invalidation Append versions instead of pages Write filled pages

14 SIAS Principle Example Tuple Append Storage Management W 1 [X 0 =9];C 1 ; W 2 [X 1 =10];C 2 ; W 3 [X 2 =11];C 3 ; Invalidation X 0 =9 X 1 =10 X 2 =11 Item X Creation T1 T2 T3 VID Map Ti P n Transaction DB Page P n X 01 2 B n Device Block B k-3 B k-2 B k-1 B k Write Order No in-place invalidation Append versions instead of pages Write filled pages DBMS specific Write reduction Simplyfied Buffer Management Significant Write Reduction (5 pages vs. 1 page) Sequentialization

15 SIAS Principle: VID map VID not explicitly stored Index to Hash Bucket No Overflow buckets VIDs are unique: one VID per tuple (data item) Storing one TID per VID (sizeof(tid)=6bytes) TIDpos=VID mod x123 0x021 0x002 Tuple X 2 Value=11 (ts create =141, VID=34) Tuple X 1 Value=10 (ts create =134, VID=34) Tuple X 0 Value=9 (ts create =123, VID=34) 0x x291 Virtual ID TupleID SIAS-Chains VID Ma p Y1 X2 Tuple Versions Y0 X1 DB - Relation X0

16 Evaluation Transaction Processing Council Benchmark C TPC-C OLTP Benchmark

17 Write reduction TPC-C OLTP benchmark Stock relation Significant reduction of host writes Random & In Place Written blocks during TPC-C TPC-C benchmark Stock relation SIAS vs. SI 2566 Page Writes! 53 Page Writes! 97% write reduction SSD Endurance? Sequentialization

18 NOTPM TPC-C: Throughput on 2x SSD RAID New Order Transactions per Minute (NOTPM) 6500 TPC-C on SSD Raid: Throughput (NOTPM) SIAS scales further >540WHs % 5000 SI: Saturated with 4500 <450 WHs SIAS-Chains SI

19 Response Time (sec.) TPC-C: Response Time on 2x SSD RAID Average response time: new order transaction TPC-C on SSD Raid: Response Time (sec.) SI: saturated 3x lower SIAS-Chains 0,274 0,711 1,5 2,179 2,931 SI 0,376 2,063 4,806 7,937 9,707 Peak Load tolerance: SIAS scales with ~540WHs

20 NOTPM TPC-C: Throughput on 6x SSD RAID (Sylt) New Order Transactions per Minute (NOTPM) TPC-C on Sylt: Throughput (NOTPM) Saturation SIAS-Chains SI SIAS removes I/O Bottleneck

21 Response time (sec.) TPC-C: Response Time on 6x SSD RAID (Sylt) Average response time of new order table TPC-C on Sylt: Response time (sec.) SIAS-Chains 0,024 0,075 0,277 3,031 5,272 10,048 SI 0,028 0,369 3,648 9,725 12,48 22,6 SI Saturation <1200WH SIAS Saturation ~1300WH

22 Contributions SIAS Architectural Changes New Version Organization VID Optimized Index One Place invalidation Chaining Selective Scan over VID map Tuple Granularity Append Storage Manager Write Retention Implementation in PostgreSQL

Thank You Publications Gottstein, Robert. Impact of New Storage Technologies on an OLTP DBMS, Its Architecture and Algorithms. Doctoral dissertation, Technische Universität Darmstadt. 2016.

23 Thank You Publications Gottstein, Robert. Impact of New Storage Technologies on an OLTP DBMS, Its Architecture and Algorithms. Doctoral dissertation, Technische Universität Darmstadt DBMS on Modern Storage Hardware (Tutorial). I. Petrov, R. Gottstein, S. Hardock. ICDE SIAS-V in Action: Snapshot Isolation Append Storage - Vectors on Flash. Robert Gottstein, Thorsten Peter, Ilia Petrov and Alejandro Buchmann. In 17th International Conference on Extending Database Technology (EDBT) Multi-Version Databases on Flash: Append Storage and Access Paths. Robert Gottstein, Ilia Petrov, Alejandro Buchmann. International Journal On Advances in Software, Vol. 6, Number 3 and Read Optimisations for Append Storage on Flash. Robert Gottstein, Ilia Petrov, Alejandro Buchmann. 17th International Database Engineering and Applications Symposium, Barcelona, Spain, ACM, (IDEAS 2013). FBARC: I/O Asymmetry-Aware Buffer Replacement Strategy. Paul Dubs, Ilia Petrov, Robert Gottstein, Alejandro Buchmann. Workshop on Accelerating Data Management Systems Using Modern Processor and Storage Architectures" (ADMS 2013), in conjunction with VLDB 2013, Riva del Garda, Trento, Italy in August Aspects of Append-Based Database Storage Management on Flash Memories. Robert Gottstein, Ilia Petrov, Alejandro Buchmann. DBKDA Best Paper Award. Append Storage in Multi-Version Databases on Flash. Robert Gottstein, Ilia Petrov, Alejandro Buchmann. 29th British National Conference on Databases, BNCOD 2013, University of Oxford, United Kingdom, SI-CV: Snapshot Isolation with Co-located Versions. Robert Gottstein, Ilia Petrov, Alejandro Buchmann. In Raghunath Nambiar, Meikel Poess: Topics in Performance Evaluation, Measurement and Characterization, Lecture Notes in Computer Science 7144, ISBN , Springer Berlin / Heidelberg, / _9 Data-Intensive Systems on Evolving Memory Hierarchies. I. Petrov, D. Bausch, R. Gottstein, A. Buchmann. EEbS Revisiting DBMS Space Management for Native Flash. S. Hardock, I. Petrov, R. Gottstein, A. Buchmann. EDBT NoFTL for Real: Databases on Real Native Flash Storage. S. Hardock, I. Petrov, R. Gottstein, A. Buchmann. EDBT NoFTL: Database Systems on FTL-less Flash Storage. Sergej Hardock, Ilia Petrov, Robert Gottstein, Alejandro Buchmann. 39th International Conference on Very Large Databases (VLDB), Riva del Garda, Italy, 2013.

SICV Snapshot Isolation with Co-Located Versions

SICV Snapshot Isolation with Co-Located Versions Robert Gottstein, Ilia Petrov, Alejandro Buchmann {lastname}@dvs.tu-darmstadt.de Databases and Distributed Systems Robert Gottstein, Ilia Petrov, Alejandro