John Dickinson gave a presentation on Swift, an open source scalable object storage system. He discussed Swift's architectural design including the proxy server, ring, storage servers, and consistency servers. He also covered Swift's history, best practices for deployment in small and large clusters, and future work including improving the ring and making deployment more modular. The presentation provided an overview of Swift's capabilities and limitations.

1. Wednesday, July 27, 11

2. Swift Overview
John Dickinson
Swift Project Technical Lead
Wednesday, July 27, 11

3. What We’ll Cover
‣ Intro to Swift
‣ Architectural Overview
‣ Best Practices for Deploying
‣ Future work
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4. Swift is Scalable Storage
‣ Scales as the cluster grows
‣ Designed to run on commodity hardware
‣ No single point of failure
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5. Swift is not
‣ RAID
‣ Distributed Filesystem
‣ CDN
‣ SAN/NAS/DAS
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6. Swift Use Cases
‣ Multi-tenant
‣ Backups
‣ Typically large
‣ Write-once, read-never
‣ Web Content
‣ Typically small
‣ Write-many, read-very-many
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7. Swift Use Cases (cont.)
‣ Document management
‣ Medical imaging
‣ Disaster recovery
‣ Caching
‣ Storage appliances
‣ Scientific data
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8. Example Usage
‣ Standard HTTP verbs
‣ Standard HTTP response codes
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9. Designing Swift
‣ At scale, everything breaks
‣ Design for failure
‣ The “Happy Path” is trivial
‣ At scale, even rare events happen a lot
‣ “Simple is better than complex.”
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10. Swift History
‣ Rackspace Cloud Files (circa 2008)
‣ Distributed Storage
‣ Centralized Metadata
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11. Swift History (cont.)
‣ Rackspace Cloud Files (circa 2010)
‣ Redesigned from the ground up
‣ Distributed storage and metadata
‣ Worked closely with ops
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12. Modular Design of Swift
‣ Proxy Server
‣ The Ring
‣ Storage Servers
‣ Consistency Servers
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13. Proxy Server
‣ Public face of swift
‣ Determines appropriate storage nodes
‣ https://swift.example.com/v1/account/container/object
‣ Coordinates responses
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14. The Ring
‣ Maps requests to storage nodes
‣ Availability zones
‣ Expandable without affecting most entities
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15. The Ring, in detail
‣ Started as a consistent-hashing ring
‣ Availability zones
‣ Became a static map of partitions to volumes
‣ What is a partition?
‣ What is a volume?
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16. Storage Servers
‣ Account server
‣ Container server
‣ Object server
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17. Storage Servers (Account and Container)
‣ SQLite databases
‣ Groups containers and objects into accounts
‣ Simple schema
‣ Table for listings
‣ Table for metadata
‣ Scale concerns?
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18. Storage Servers (Object)
‣ Use the file system to store files
‣ Any file system that supports xattrs
‣ Files named by timestamp
‣ Tombstones
‣ Directory structure
‣ /mount/data_dir/partition/hash_suffix/hash/object.ts
‣ Directory metadata can easily exhaust RAM
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19. Consistency Servers
‣ Replicators
‣ Updaters
‣ Auditors
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20. How to Deploy
‣ Swift All-In-One (SAIO)
‣ Small cluster
‣ Large cluster
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21. How to Deploy (SAIO)
‣ All services in one VM
‣ Use loopback devices for storage
‣ Great for dev work and validation testing
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22. How to Deploy (Small Cluster)
‣ Two load-balanced proxies
‣ Five storage nodes
‣ This area needs work
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23. How to Deploy (Large Cluster)
‣ Five zones
‣ Two proxies per zone
‣ Many storage nodes per zone
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24. How to Deploy (Large Cluster, networking)
‣ 10g external network
‣ 1g (or 10g) internal network
‣ Use-case concerns
‣ Internal proxy network divided by replica count
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25. How to Deploy (Large Cluster, IO)
‣ Dedicated Container and Account servers
‣ Few, relative to object servers
‣ Many IOPS (i.e. SSDs)
‣ Cheap storage for Object servers
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26. Future Dev Work
‣ Better Ring
‣ Layered zones
‣ Unique-of-zones-as-possible
‣ Tiered storage
‣ More modular deployment
‣ Cabinets, not zones
‣ More features
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27. What Swift is “Missing”
‣ Auth
‣ ID management
‣ Stats
‣ Quotas
‣ Billing
‣ CDN
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28. Questions?
‣ #openstack on freenode
‣ http://launchpad.net/swift
‣ http://d.not.mn/swift_overview_oscon2011.pdf
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29. John Dickinson
‣ @notmyname
‣ http://gplus.to/notmyname
‣ me@not.mn
‣ http://not.mn
Wednesday, July 27, 11