CASSANDRA MEETUP - Choosing the right cloud instances for success

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Apache Cassandra™ Choosing instances for success

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Erick Ramirez DataStax Engineering

@flightc

Welcome• Your app in focus — reads vs writes, CPU vs RAM• What IOPS? How much is enough?• Are ephemeral disks evil?• False economy — cheaper instances can cost you more• A time to kill — they’re not your pets

© DataStax, All Rights Reserved.3



https://academy.datastax.com

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ONE SIZE DOES NOTFIT ALL

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Tailor to workload

• intimately understand your app• reads vs writes• CPU vs memory• OLTP vs OLAP• use case will dictate requirements


STORAGE OPTIONS

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EBS gp2 SSDs

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• general purpose EBS option• persistent (durable)• default volume for EC2 instances• guaranteed 99% single-digit millisecond latency• only pay for each GB (IOPS included)• minimum 10K IOPS for production workloads

3 IOPS/GB (3K IOPS/TB)

Max 10K IOPS/vol

Max 160MB/s throughput/vol

1TB = $122/mo, $1474/yr


EBS io1 SSDs

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• fastest available EBS option• persistent (durable)• for latency-sensitive OLTP workloads• guaranteed 99.9%* single-digit millisecond latency• provisioned IOPS are charged extra• minimum 10K IOPS for production workloads

* read the fine print

Up to 50 IOPS/GB

Max 20K IOPS/vol

Max 320MB/s throughput/vol

1TB = $141/mo, $1695/yr

1K IOPS = $72/mo, $864/yr


#spoileralertEPHEMERAL IS YOUR FRIEND

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Ephemeral storage

• performance orders of magnitude better than EBS• already included in instance costs, e.g. m3, c3, i3

• “physically” attached• not durable across reboots but…


HELLO, CASSANDRA

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What is Cassandra

• massively scalable NoSQL database• fully distributed, no single-point-of-failure• linear horizontal scaling


Why Cassandra

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• all nodes are the same — no SPOF• real-time, durable writes• linear scaling on commodity servers• real-time replication across data centres• always on — no offline operation• because you have a scale problem


Replication across DCs


CHEAP INSTANCESMAY BE COSTING YOU

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Real example

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• deployed on c4.4xlarge

• using EBS io1 with 3K PIOPS• nodes dropping writes• high read latencies

16 vCPU, 30GB RAM

Instance $ 5443EBS io1 1TB $ 1695PIOPS 3K $ 2592 ————————Annual cost $ 9730


Recommendation

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• swap to i3.2xlarge

• 1.9TB NVMe SSDs included• 3M IOPS, 16GB/s• 60-70% cheaper than replaced i2.2xlarge

8 vCPU, 61GB RAM

Instance $ 4174 ————————Annual cost $ 4174


HORSES FOR COURSES

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Use case - dev, light prod

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• m3.large suitable

• entry-level load, testing-the-waters• minimum 3 C* nodes with RF=3• use CMS GC with 2GB heap

2 vCPU7.5GB RAM1 x 32GB SSD

$ 962/yr


Use case -low prod volume

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• m3.xlarge suitable

• JVM will perform better with the extra RAM• min 3 C* nodes with RF=3• use CMS GC with 8GB heap

4 vCPU15GB RAM1 x 40GB SSD

$ 1924/yr


Use case -moderate prod volume

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• c3.2xlarge recommended

• more diskspace, extra cores a bonus• costs 50% more for 2x CPU and 4x diskspace• min 3 C* nodes with RF=3• use CMS GC with 8GB heap

8 vCPU15GB RAM2 x 80GB SSD

$ 2916/yr


Use case -real prod volume

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• i3.2xlarge recommended

• will handle all kinds of workloads including Analytics, Graph and Search (Solr)

• min 3 C* nodes with RF=3• use G1 GC with 24GB heap (32GB for Search nodes)

8 vCPU61GB RAM1.9TB NVMe SSD

$ 4174/yr


https://datastaxacademy.slack.com

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Thank you

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Technology

CASSANDRA MEETUP - Choosing the right cloud instances for success