Swift Architecture and Practice, by Alex Yang
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The document discusses the principles, architecture, and practice of Swift object storage at SinaAppEngine. It describes how Swift provides high reliability through consistent hashing, replication across multiple zones, and an eventual consistency model. It outlines SinaAppEngine's implementation of Swift for storage, including authentication, quotas, and domain remapping. Problems addressed include improving replication efficiency and SQLite performance as well as controlling rsync bandwidth. The document provides an overview of how Swift storage works at scale.
Swift Architecture and Practice, by Alex Yang
- 1. 架构与实践 Swift 在这里写上你的标题 @SinaAppEngine 副标题文字副标题文字 杨雨 /2012-08-日 作者名字 / 11 期
- 2. Content 1 Principles and Architecture 写上你的文字你的文字 00 2 The Practice of Swift @SinaAppEngine 01 02 3 Problems and Imporvemetns 03 04 05
- 3. Storage Types Types Protocol Application 00 写上你的文字你的文字 Block Storage SATA, SCSI, iSCSI SAN, NAS, EBS 01 File Storage Ext3/4, XFS, NTFS PC, Servers, NFS 02 Object Storage HTTP, REST Amazon S3, 03 Google Cloud Storage, Rackspace Cloud Files 04 Specific Storage Specific protocol MySQL, MongoDB, 05 based on tcp HDFS
- 4. Storage Types 00 写上你的文字你的文字 01 02 03 04 05 From: http://www.buildcloudstorage.com/2012/08/is-openstack-swift-reliable-enough-for.html
- 5. Targets •High Reliability = High Durability + High Availability •High Durability - Replicas and Recovery •High Availability - Replicas and Partition •Low Cost - Commodity Hardware •Scale Out - No Single Bottleneck, Share Nothing
- 7. Reliability Consistent Hashing with Virtual Node
- 8. Reliability Consistent Hashing with Virtual Node
- 9. Reliability The advantages of consistent hashing: 1.Metadata is small;(AWS S3 has 762 billion objects) 2.Distribution unformity; 3.Peer to perr comunication; 4.Load blance.
- 10. Reliability •Virtual node(partition) - Object distribution uniformity •Weight - Allocate partitions dynamically •Zone - Partition Tolerance Zones can be used to group devices based on physical locations, power separations, network separations, or any other attribute that would lessen multiple replicas being unavailable at the same time. Swift ： Ring - The index file for locating object in the cluster.
- 11. Reliability
- 12. Reliability Durability: 99.999..9%? AWS S3 with 99.999999999% •Annualized failure rate of devices.(disk, network...) •Bit rot rate and the time to detect bit rot. •Mean time to recovery. •More about durability ： http://www.buildcloudstorage.com/2012/08/is-openstack-swift- reliable-enough-for.html Swift ： Auditor - To detect bit rot; Replicator-To keep the consistency of object;
- 14. Consistency Model Quroum + Object Version + Async Replicatiton Quroum Protocol: N, the number of nodes that store replicas of the data; W, the number of replicas that need to acknowledge the receipt of the update before the update completes; R, the number of replicas that are contacted when a data object is accessed through a read operation; If W+R>N, then the write set and the read set always overlap and one can guarantee strong consistency. In Swift, NWR is configurable. General configuration: N=3, W=2, R=1 or 2, So the swift can providetwo models of consistency, strong and eventual.
- 15. Consistency Model Weak Consistency （ N=3,W=2,R=1 ）
- 16. Consistency Model Strong Consistency （ N=3,W=2,R=2 ）
- 17. Consistency Model Special Scene ： dirty read
- 19. Metadata account |-- container1 |------obj1 |------obj2 |-- container2 |------objN How to store the relationship of account, container and object? •Relation Database •NoSQL, Cassandra, MongoDB •Relation Datatbase with Sharding
- 20. Metadata The target of swift: no single failure, no bottletneck, scale out The Swift way: sqlite + consistent hashing + quroum A sqlite db file is an object. So the database is HA, durable and with eventual consistency.
- 22. Architecture
- 25. Our Works •Swift as the SAE Storage -Auth module for SAE(Key-Pair) -Keystone for SAE(Token) -HTTP Cache-Control module -Quota(limit the number of containers and objects, limit the storage usage) -Domain remap app-domain.stor.sinaapp.com/obj To sinas3.com/v1/SAE_app/domain -Rsync with bwlimit -Billing -Storage Firewall •Swift as the SWS Simple Storage Service -Container unique module container.sinas3.com/object -Keystone middleware for auth protocol converting
- 26. Our Steps for Switching SAE Storage •Bypass test one month online( 旁路读写测试 ) •Switch step by step one month( 灰度切换 ) •Ops Monitoring: I/O, CPU, Memery, Disk LogCenter: syslog-ng, statistics and analytics
- 30. Problems&Imporvements The async processor for keeping eventual consistency is inefficient. Replicator, auditor, container-updater Logic: loop all objects or dbs on disk, query replica's server to determin whether to sync. Results: High I/O; High CPU usage; Stress on account/container/object- servers, impact the availability; Long time for eventual consistency, impact the durability; The list operation is not consistent. How to improvements? 1.Runing replicator, auditor and container updater during idle time; 2.An appropriate deployment; 3.A new protocol for keeping relplica's consistency; (based on log and message queue) 4.Adding new nodes, scale out.
- 31. Problems&Imporvements The performance of sqlite. Quota for objects and containers Running sqlite on the high performance I/O devices The bandwidth of rsync is not under control. Out-of-band management Add bandwidth limitations for rsync Database centralized or distributed?
- 33. Q&A Weibo: @AlexYang_Coder Email: [email protected] GTalk: [email protected] Blog: http://alexyang.sinaapp.com