Say Hello to MyRocks
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This document provides an overview of MyRocks, a storage engine for MySQL/MariaDB that uses the RocksDB key-value store. It discusses the write amplification issues with InnoDB, how LSM trees in RocksDB address these issues through log-structured merging, and benchmarks showing the size, write amplification, and performance improvements MyRocks provides over InnoDB. It also outlines the process of integrating MyRocks into MariaDB, current status as an alpha plugin, and plans to improve support and testing.
![42
“Is it stable”?
● The components are stable
– (MyRocks + RocksDB) are run in
production @ Facebook
– RocksDB is also used elsewhere
– MyRocks not much. yet.
● Connections with MariaDB
– Some are stable
– Some are [nearly] missing
MyRocks
MariaDB
RocksDB](https://image.slidesharecdn.com/m17-say-hello-to-myrocks-170412210557/85/Say-Hello-to-MyRocks-42-320.jpg)
Say Hello to MyRocks
- 1. Say Hello to MyRocks Sergei Petrunia | Senior Software Engineer, MariaDB [email protected] M|17, April 11-12th , 2017
- 2. 2
- 3. 3 What can be done about this?
- 4. 4 Data vs Disk Put some data into the database How much is written to disk? INSERT INTO tbl1 VALUES ('foo') amplification = size of data size of data on disk
- 5. 5 Amplification Write amplification Space amplification Read amplification amplification = size of data size of data on disk foo
- 6. 6 Amplification in InnoDB ● B*-tree ● Read amplification – Assume random data lookup – Locate the page, read it – Root page is cached ● ~1 disk read for the leaf page – Read amplification is ok
- 7. 7 Write amplification in InnoDB ● Locate the page to update ● Read; modify; write – Write more if we caused a page split ● One page write per update! – page_size / sizeof(int) ● Write amplification is an issue.
- 8. 8 Space amplification in InnoDB ● Page fill factor <100% – to allow for updates ● Compression is done per-page – Compressing bigger portions would be better – Page alignment ● Compressed to 3K ? Still on 4k page. ● => Space amplification is an issue
- 9. 9 InnoDB amplification summary ● Read amplification is ok ● Write and space amplification is an issue – Saturated IO – Faster SSD wear out – Need more space on SSD ● => Low storage efficiency
- 10. LSM tree
- 11. 11 Log-structured merge tree ● Writes go to – Log – MemTable ● MemTable is flushed to SortedStringTable ● Writing 2x – But only useful data MemTableWrite Log SST MemTable
- 12. 12 Log-structured merge tree ● Writing produces more SSTs ● SSTs are immutable ● SSTs may have multiple versions of data MemTableWrite Log SST MemTable SST ...
- 13. 13 Reads in LSM tree ● Need to merge the data on read – Read amplification suffers ● Should not have too many SSTs. MemTable Read Log SST MemTable SST ...SST
- 14. 14 Compaction ● Merge multiple SSTs into one ● Removes old data versions ● Reduces the number of files ● Write amplification++ :-( SST SST . . .SST SST
- 15. 15 Compaction considerations ● Find the sweetspot – Reduce # SSTs – Don’t compact too often ● Be efficient – Compact files of similar size – Remove duplicate versions asap ● Many strategies – Leveled – Size-tiered SST SST . . .SST SST – ...
- 16. 16 Leveled Compaction a-c a-f . . . . . . . . . . . . b-gL0 L1 a-e f-i j-n o-z L2 a-b c-g f-k l-q L7 a-c d-f g-l q-z MemTable q-z 5 mb 50 mb 500 mb
- 17. 17 Leveled Compaction MemTable a-c a-f . . . . . . . . . . . . b-gL0 L1 a-e f-i j-n o-z L2 a-b c-g f-k l-q L5 a-c d-f g-l q-z q-z 5 mb 50 mb 500 mb read(‘f’)
- 18. 18 Leveled Compaction MemTable a-c a-f . . . . . . . . . . . . b-gL0 L1 a-e f-i j-n o-z L2 a-b c-g f-k l-q L5 a-c d-f g-l q-z q-z 5 mb 50 mb 500 mb
- 19. 19 Leveled Compaction MemTable a-c a-f . . . . . . . . . . . . bL0 L1 a-e f-i j-n o-z L2 a-b c-g f-k l-q L5 a-c d-f g-l q-z q-z 5 mb 50 mb 500 mb
- 20. 20 LSM Tree summary ● LSM architecture – Data is stored in log, then SST files – Writes to SST files are sequential, efficient ● Better compression – Have to read from multiple SST files – Compaction process merges SST files ● Efficiency – Write amplification is reduced – Space amplification is reduced – Read amplification increases
- 21. RocksDB
- 22. 22 RocksDB ● “An embeddable key-value store for fast storage environments” ● Uses LSM architecture – Leveled compaction – Server-grade ● Initially a fork of LevelDB ● Developed at Facebook – First release in 2012 – Used at Facebook and many other companies
- 23. 23 RocksDB properties ● Embedded library ● Stores (key, value) pairs – No data types – No secondary indexes – No SQL-like tables ● Column Families = tablespaces ● No replication support – There is a 3rd-party addon ● Efficient, but hard to work with
- 24. MyRocks
- 25. 25 MyRocks ● A MySQL storage engine ● Uses RocksDB for storage ● Implements a MySQL storage engine on top – Secondary indexes – Data types – SQL transactions – … ● Developed* and used by Facebook – *-- with some MariaDB involvement
- 26. 26 Size amplification benchmark ● Benchmark data and chart from Facebook ● Linkbench run ● 24 hours
- 27. 27 Write amplification benchmark ● Benchmark data and chart from Facebook ● Linkbench
- 28. 28 QPS ● Benchmark data and chart from Facebook ● Linkbench
- 29. 29 QPS on in-memory workload ● Benchmark data and chart from Facebook ● Sysbench read-write, in-memory ● MyRocks doesn’t always beat InnoDB
- 30. 30 QPS ● Benchmark data and chart from Facebook ● Linkbench
- 31. 31 A real efficiency test For a certain workload we could reduce the number of MySQL servers by 50% – Yoshinori Matsunobu
- 32. 32 Another write amplification test ● InnoDB vs ● MyRocks serving 2x data InnoDB 2x RocksDB 0 4 8 12 Flash GC Binlog / Relay log Storage engine
- 33. 33 Cumulative response time 0 50000 100000 150000 200000 250000 300000Kilo-Queries RocksDB x2 InnoDB
- 34. 34 CPU usage is higher with MyRocks Time InnoDB 2x RocksDB 100% 0% 80% 50-60%
- 35. 35 MyRocks limitations ● Transactional storage engine – REPEATABLE READ, READ COMMITTED – No SERIALIZABLE ● Must use Row-based-Replication ● No cross-engine transactions ● Transaction must fit in memory ● Online DDL more limited than InnoDB
- 36. 36 MyRocks availability ● Part of github.com/facebook/mysql-5.6 ● No binaries ● No packages ● Facebook’s branch of MySQL – Special extensions – Special ways to compile, run tests, etc ● Not easy to use
- 38. 38 MyRocks in MariaDB ● New technology ● Built and used at Facebook’s scale ● Adoption ● Packaging ● Community ● MariaDB features ● ...
- 39. 39 Getting MyRocks into MariaDB ● Port MyRocks into MariaDB 10.2 – Decouple it from facebook/mysql-5.6 features – Make it work with MariaDB’s features ● Set up a merge process – Need to follow Facebook’s progress ● Setup the process to build packages ● Documentation ● Expertise ● ...
- 40. 40 Getting MyRocks into MariaDB ● Port MyRocks into MariaDB 10.2 – Decouple it from facebook/mysql-5.6 features – Make it work with MariaDB’s features ● Set up a merge process – Need to follow Facebook’s progress ● Setup the process to build packages ● Documentation ● Expertise ● ... ✘ ✔ ✘ ✘✔ ✔ ✔ ✔
- 41. 41 Current status ● “MariaDB 10.2.5 RC includes an ALPHA version of MyRocks storage engine” ● It’s a loadable plugin (ha_rocksdb.so) ● Packages – Bintar, deb, rpm, win64 zip + MSI – Recent versions of OS due to compilers for RocksDB’s requirements ● Not all features work yet – Optimizer and SQL features work – Replication/binlog features don’t work yet.
- 42. 42 “Is it stable”? ● The components are stable – (MyRocks + RocksDB) are run in production @ Facebook – RocksDB is also used elsewhere – MyRocks not much. yet. ● Connections with MariaDB – Some are stable – Some are [nearly] missing MyRocks MariaDB RocksDB
- 43. 43 Plans ● Finish the missing pieces – Storage Engine + binlog ● Improve support for multiple SEs – MDEV-12179 ● Increase maturity – Pass the tests – More test coverage – Benchmarks ● Documentation MyRocks MariaDB RocksDB
- 44. 44 References ● https://www.slideshare.net/profyclub_ru/making-the-case-for-writeoptimized-da tabase-algorithms-mark-callaghan-facebook ● https://code.facebook.com/posts/190251048047090/myrocks-a-space-and-write -optimized-mysql-database ● https://www.facebook.com/atscaleevents/videos/1775545312718565/ ● ... Further information ● 10.00 Real World: Deploying MyRocks in Production at Facebook, Yoshinori Matsunobu ● http://myrocks.io ● https://mariadb.com/kb/en/mariadb/myrocks-in-mariadb/
- 45. Thanks! Q&A