This document summarizes an introduction to Cassandra and Linux. It discusses Cassandra's origins from Amazon's Dynamo and Google's BigTable systems. It also outlines key features of Cassandra like availability, scalability, performance and data center support. The document provides hardware recommendations for Cassandra including memory, CPU, disks and configuration guidance. It concludes by listing resources for learning more about Cassandra.

1. Cassandra and Linux
An Introduction
Nick Bailey
@nickmbailey
nick@datastax.com
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Background
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Analytics
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Real Time
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Big Data
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Dynamo
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BigTable
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Who is using it?
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Why do people like Cassandra?
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Availability
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http://techblog.netflix.com/2012/07/lessons-netflix-learned-from-aws-storm.html
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Scalability
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http://techblog.netflix.com/2011/11/benchmarking-cassandra-scalability-on.html
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Performance
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http://vldb.org/pvldb/vol5/p1724_tilmannrabl_vldb2012.pdf
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Multi Datacenter Support
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Hadoop Support
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Hadoop Support
• Data Locality
• Workload Partitioning
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Architecture - Cluster
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Architecture - Node
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Writes
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Writes
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Reads
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Reads
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Compaction
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Compaction
• Periodically merge sstables
• Multiple strategies
• SizeTieredCompaction
• LeveledCompaction
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Hardware
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Remember:
Cassandra scales horizontally
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Memory
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Memory
• More is better
• Sweet spot: 16-64GB
• Don’t give it all to the JVM
• Generally no more than 8GB
• Rest for page cache
• Can run with less for quick testing
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CPU
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CPU
• Cassandra is almost always IO bound
• Sweet spot: 8 cores
• Additional CPU required for:
• compression
• leveled compaction
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Disks
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Disks
• SSDs are awesome, not required
• Without SSDs:
• At least 2 disks (commitlog, data) (more on that later)
• Faster is better
• Before Cassandra 1.2: ~500GB per node
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A Note on SSDs
• Write Amplification
• http://en.wikipedia.org/wiki/Write_amplification
• Consumer grade SSDs are fine
• See talk by Rick Branson for more
• http://www.youtube.com/watch?v=zQdDi9pdf3I
• http://www.slideshare.net/rbranson/cassandra-and-
solid-state-drives
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Homogenous Nodes
• Usually, keep nodes the same
• Vnodes
• Make heterogenous clusters easier
• Added in version 1.2
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Configuration
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Disks
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Commit Log
• Keep separate from data drives
• Caveats
• SSDs
• Virtualized Environments
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Data Drives
• Before Cassandra 1.2
• RAID0/RAID10
• Cassandra 1.2
• JBOD
• Configuration options: stop/best_effort
• XFS
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Note on SAN/NAS
• Don’t use them
• Cassandra is already distributed
• SPOF
• Cassandra is already IO bound
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Firewall
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Firewall
• Ports:
• 7000 - cluster communication
• 9160 - client communication
• JMX:
• Unfortunately, the JMX protocol sucks
• Ports 7199 and 1024+ for remote access
• Solution: only access JMX locally
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Virtualized Environments (EC2)
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EC2
• Large/XLarge instances
• Don’t use EBS
• phi_convict_threshold
• Don’t fix nodes, Replace them
• DataStax provides an AMI
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Miscellaneous
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Swap
• Disable it
• sudo swapoff --all
• JVM swaps to disk, Cassandra explodes
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Limits
• /etc/security/limits.conf
• nofile
• memlock
• as
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NTP
• Install it on
• Cassandra Servers
• Clients
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Monitor your cluster!
• Cassandra exposes tons of metrics
• Via JMX
• Recently, more options available
• DataStax OpsCenter
• http://www.datastax.com/what-we-offer/products-
services/datastax-opscenter
• Or integrate with your own system
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Don’t use Windows
• I’m not presenting at Texas Windows Fest
• Technically supported
• Not widely deployed
• Reduced performance
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Resources
• http://www.datastax.com/docs
• #cassandra on freenode
• http://www.planetcassandra.org
• Mailing Lists
• http://cassandra.apache.org to subscribe
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Or...
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54. Come to the Summit!
Ask me for a discount code (nick@datastax.com)
June 11-12, 2013
San Francisco, CA
http://www.datastax.com/company/news-and-events/events/
cassandrasummit2013
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55. Want a job?
http://www.datastax.com/company/careers
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56. Questions?
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