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Wednesday, July 27, 11
Swift Project Technical LeadJohn Dickinson
Swift Overview
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What We’ll Cover
‣ Intro to Swift‣ Architectural Overview‣ Best Practices for Deploying‣ Future work
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Swift is Scalable Storage
‣ Scales as the cluster grows‣ Designed to run on commodity hardware‣ No single point of failure
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Swift is not
‣ RAID‣ Distributed Filesystem‣ CDN‣ SAN/NAS/DAS
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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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Swift Use Cases (cont.)
‣ Document management‣ Medical imaging‣ Disaster recovery‣ Caching‣ Storage appliances‣ Scientific data
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Example Usage
‣ Standard HTTP verbs‣ Standard HTTP response codes
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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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Swift History
‣ Rackspace Cloud Files (circa 2008)‣ Distributed Storage
‣ Centralized Metadata
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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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Modular Design of Swift
‣ Proxy Server‣ The Ring‣ Storage Servers‣ Consistency Servers
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Proxy Server
‣ Public face of swift‣ Determines appropriate storage nodes‣ https://swift.example.com/v1/account/container/object
‣ Coordinates responses
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The Ring
‣ Maps requests to storage nodes‣ Availability zones‣ Expandable without affecting most entities
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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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Storage Servers
‣ Account server‣ Container server‣ Object server
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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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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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Consistency Servers
‣ Replicators‣ Updaters‣ Auditors
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How to Deploy
‣ Swift All-In-One (SAIO)‣ Small cluster‣ Large cluster
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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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How to Deploy (Small Cluster)
‣ Two load-balanced proxies‣ Five storage nodes‣ This area needs work
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How to Deploy (Large Cluster)
‣ Five zones‣ Two proxies per zone‣ Many storage nodes per zone
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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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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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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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What Swift is “Missing”
‣ Auth‣ ID management
‣ Stats‣ Quotas
‣ Billing
‣ CDN
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Questions?
‣ #openstack on freenode‣ http://launchpad.net/swift‣ http://d.not.mn/swift_overview_oscon2011.pdf
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John Dickinson
‣ @notmyname‣ http://gplus.to/notmyname‣ [email protected]‣ http://not.mn
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