mThomas Vachon • September 2012Cassandra on Openstack and AWS

presenting toBoston Cassandra

Users Group

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Agenda

• Current Openstack Implementation• Running Cassandra on Openstack• Lessons Learned about Cassandra on AWS• Connecting Openstack and AWS• Connecting Cassandra on Openstack and AWS• Questions• Show & Tell

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Current Cassandra Implementation (AWS)

• 9 Cassandra Nodes (3 per AZ)• Cassandra 1.0.10• AWS m1.xlarge – 4 Drive RAID-0 Array• EC2Snitch• RF = 3• Network Topology Aware

• Statistics• Peak Traffic: 724 r/s with 1308 wr/s across the cluster

• 3.5ms read latency avg• 1.7ms write latency avg

INTRODUCTION

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Running Cassandra on Openstack

• Ec2Snitch doesn’t work (looks to the wrong endpoint)• Its hard to guarantee you keep your instances on separate machines

with a single zone• Contention/Steal is more easily achieved due to KVM and the lack of

CPU throttling• As always, the faster the hardware, the better the performance

• Perf Test - 5 Cassandra Nodes with RF=3 (cassandra-stress)• Read/s: 1,562 w/s• Writes/s: 3,846 r/s• Avg latency per op: 7.2ms• Seems to hurt the testing server more than the Cassandra Cluster

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Lessons Learned with Cassandra and AWS

• Be proactive in adjusting your caches• Row cache is a great thing (keep it out of heap)• Key cache hit rates dictate if you should burn memory on them or not• KNOW your Data and Access Patterns

• A slow node is worse than a dead node• CPU Steal is your mortal enemy

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Connecting Openstack and AWS

• Two Options• Public Internet Replication (SSL Highly recommended)

• HUGE transfer costs, risky

• VPC Tunnel• Static Tunnel with ASA – ASA’s can only connect to one tunnel at a time even in an HA

pair• BGP Tunnel with Routing – Each router connects to two endpoints, HSRP between,

extremely redundant

• Openstack Complexity – VLAN Tagging• If using VLAN tagging in Openstack, your tunnel device needs to participate in the

VLAN which is used for VM’s (300 by default)

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Connecting Cassandra

• Since EC2Snitch doesn’t work in OS, RackInferringSnitch must be used

• Standard Multi-datacenter tokenization strategies are required• Replication lag is dependant on connectivity and latency• Tests from VPC IPSec tunnels in NJ show 8ms to Ashburn• Tests from Ashburn DC datacenters are about 4ms• The biggest problem is the volume of data and a hard cutover

• We started in EC2, but are migrating to VPC

m Questions/Suggestions?

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m P.S. - We are HIRING!

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mCome see our Openstack cluster

Show & Tell

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