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7 Deadly Sins for Cassandra OpsRachel Pedreschi
DSE Evangelist, Datastax
2© 2015. All Rights Reserved.
Lust
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#1 USE THE SIMPLE SNITCH
So many snitches…
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• SimpleSnitch • RackInferringSnitch • PropertyFileSnitch • GossipingPropertyFileSnitch • Ec2Snitch • Ec2MultiRegionSnitch • GoogleCloudSnitch • CloudstackSnitch
Switching snitches
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If the topology of the network has changed: -Shut down all the nodes, then restart them. -Run a sequential repair and nodetool cleanup on each node.
DOWNTIME ALERT!!!!
Greed
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#3 NOT UNDERSTANDING
REPAIR
Repair options
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repair (default, check your version!) repair -pr (only repair the primary range) repair -inc (only new data that has not previously been repaired) sequential repair (creates snapshots) parallel repair uses replica not being repaired
Envy
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#3 CHOOSE THE WRONG
COMPACTION STRATEGY FOR
YOUR WORKLOAD
Sized Tiered
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SST1 SST1 SST2 SST1 SST2 SST3 SST1 SST2 SST3 SST4 SST5
FLUSHFLUSH
FLUSH FLUSH
COMPACT
SST5 SST6 SST5 SST6 SST7 SST5 SST6 SST7 SST8 SST5 SST10
FLUSH FLUSH FLUSH
SST5 SST6 SST7 SST8
FLUSH
SST9
COMPACT
Compacts a set number of SSTables into a single, larger SSTable
Leveled
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Level 0
Level 1
10
Level 2100
Level 3
1,000
Level 410,000
Level 5100,000
… Level 6, 7, etc.
Date Tiered
11© 2015. All Rights Reserved. https://labs.spotify.com/2014/12/18/date-tiered-compaction/
Gluttony
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#4 CHOOSING THE WRONG
HARDWARE
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CPU
RAM
DISK
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• 2 socket, ECC memory • 16GiB minimum, prefer 32-64GiB, over 128GiB and Linux will need
serious tuning
• SSD where possible, Samsung 840 Pro is a good choice, any Intel is fine
• NO SAN/NAS, 20ms latency tops • if you MUST (and please, don’t) dedicate spindles to C* nodes, use
separate network
• Avoid disk configurations targeted at Hadoop, disks are too slow
Sloth
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#5 NOT TUNING YOUR OS
/etc/rc.local
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ra=$((2**14))# 16kss=$(blockdev --getss /dev/sda)blockdev --setra $(($ra / $ss)) /dev/sda
echo 128 > /sys/block/sda/queue/nr_requestsecho deadline > /sys/block/sda/queue/schedulerecho 16384 > /sys/block/md7/md/stripe_cache_size
/etc/sysctl.conf
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fs.file-max = 1048576vm.max_map_count = 1048576net.core.rmem_max = 16777216net.core.wmem_max = 16777216net.ipv4.tcp_rmem = 4096 65536 16777216net.ipv4.tcp_wmem = 4096 65536 16777216vm.swappiness = 1
Wrath
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#6 OVER OR UNDERSIZING
YOUR JVM
G1 or CMS?
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• Cassandra 8150 vs 7486 • Larger heap? Look into using G1 • Read the Docs • Test, test and did I mention, test?
Pride
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#7 NOT STRESS TESTING
cassandra-stress .yaml (>= 2.1)
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1. DDL – for defining your schema 2. Column Distributions – for defining the shape and size of each
column globally and within each partition 3. Insert Distributions – for defining how the data is written during the
stress test 4. DML – for defining how the data is queried during the stress test
Recommended Sessions
22© 2015. All Rights Reserved.
DataStax Making Cassandra Fail (for effective testing) 3:30 Thursday Ballroom H
Pythian Manage your compactions before they manage you 4:20 Ballroom H
The Last Pickle Steady State Data Size with Compaction, Tombstones, and TTL 4:20 Great America #2 Wednesday
Crowdstrike, Inc. Real World DTCS For Operators
Thank you@RachelPedreschi
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