Cassandra multi-datacenter operations essentials

Cassandra multi-datacenter operations essentials
Apache: Big Data 2016 - Vancouver, CA
Julien Anguenot (@anguenot)

agenda
• key notions
• configuration and tuning
• tools and operations
• monitoring
• things you need to know
2

this talk covers versions…
• 2.0.x
• 2.1.x
• 2.2.x
• 3.0.x
3

this talk does not cover…
• general Cassandra data modeling
• authentication / authorization
• AWS
• Windows
• versions >= 3.1 and new “tick-tock” release process
• DSE
• and a lot more …
4

iland cloud?
• cloud provider (compliance, advanced security, multi-DC world wide)
• using C*, since version 1.2, as a foundation for our data warehouse
and platform
• cloud analytics (compute, storage, network, etc.)
• “real-time” and historical data
• billing, alerts, user configuration, etc.
• sole record-keeper
• http://www.slideshare.net/anguenot/leveraging-cassandra-for-realtime-
multidatacenter-public-cloud-analytics
• www.iland.com
5

what is Cassandra?
• distributed partitioned row store
• physical multi-datacenter native support
• tailored (features) for multi-datacenter deployment
7

why multi-datacenter deployments?
• multi-datacenter distributed application
• performances
read / write isolation or geographical distribution
• disaster recovery (DR)
failover and redundancy
• analytics
8

9
cluster
datacenter(s)
rack(s)
server(s)
Vnode(s)
Cassandra hierarchy of elements

Cassandra cluster
• the sum total of all the servers in your database
throughout all datacenters
• span physical locations
• defines one or more keyspaces
• no cross-cluster replication
10

Cassandra datacenter
• grouping of nodes
• synonymous with replication group
• a grouping of nodes configured together for replication
purposes
• each datacenter contains a complete token ring
• collection of Cassandra racks
11

Cassandra rack
• collection of servers
• at least one (1) rack per datacenter
• one (1) rack is the most simple and common setup
12

Cassandra server
• Cassandra (the software) instance installed on a machine
• AKA node
• contains 256 virtual nodes (or Vnodes) by default
13

Virtual nodes (Vnodes)
• C* >= 1.2
• data storage layer within a server
• tokens automatically calculated and assigned
randomly for all Vnodes
• automatic rebalancing
• no manual token generation and assignment
• default to 256 (num_tokens in cassandra.yaml)
14

Vnodes and consistent hashing
• allows distribution of data across a cluster
• Cassandra assigns a hash value to each partition key
• each Vnode in the cluster is responsible for a range of
data based on the hash value
• Cassandra places the data on each node according
to the value of the partition key and the range that the
node is responsible for
16

partition
• individual unit of data
• partitions are replicated across multiple Vnodes
• each copy of the partition is called a replica
17

partitioner (1/2)
• partitions the data across the cluster
• function for deriving a token representing a row from
its partition key
• hashing function
• each row of data is then distributed across the cluster by
the value of the token
18

partitioner (2/2)
• Murmur3Partitioner (default C* >= 1.2) 
uniformly distributes data across the cluster based on
MurmurHash hash values
• RandomPartitioner (default C* < 1.2) 
uniformly distributes data across the cluster based on MD5
hash values
• ByteOrderedPartitioner (BBB) 
keeps an ordered distribution of data lexically by key bytes
19

keyspace (KS)
• namespace container that defines how data is
replicated on nodes
• cluster defines KS
• contains tables
• defines the replica placement strategy and the
number of replicas
24

data replication
• process of storing copies (replicas) on multiple nodes
• KS has a replication factor (RF) and replica placement strategy
• max (RF) = max(number of nodes) in one (1) data center
• data replication is defined per datacenter
25

replica placement strategy
there are two (2) available replication strategies:
1. SimpleStrategy (single DC)
2. NetworkTopologyStrategy (recommended cause easier to expand) 
choose strategy depending on failure scenarios and application needs
for consistency level
26

Consistency level
• how many nodes must ACK operation at client level?
• tunable consistency at client level
• ANY
• ONE
• ALL
• QUORUM / LOCAL_QUORUM (DC only)
• SERIAL and conditional updates (IF DOES NOT EXIST)
27

local_quorum examples
• nodes=3, RF=3 - can tolerate 1 replica being down
• nodes=5, RF=3 - can tolerate 2 replica being down
• etc.
28

snitch (1/2)
• determines which data centers & racks nodes belong to
• informs Cassandra about the network topology
• effective routing
• replication strategy places the replicas based on
snitch
29

snitch (2/2)
• SimpleSnitch 
single DC only
• GossipingPropertySnitch 
cassandra-rackdc.properties
• PropertyFileSnitch 
cassandra-topology.properties
• RackInferringSnitch 
determined by rack and data center, which are 3rd and 2nd octet
of each node’s IP respectively
30

snitch (3/3)
• more deployment specific snitches for EC2, Google,
Cloudstack etc.
31

Gossip
• peer-to-peer communication protocol
• discover and share location and state information about
the other nodes in a Cassandra cluster
• persisted by each node
• nodes exchange state messages on regular basis
32

seed node
• bootstrapping the gossip process for new nodes joining
the cluster
• use the same list of seed nodes for all nodes in a cluster
• include at least one (1) node of each datacenter in seeds
list
33

Essentially, …
• sequential writes in commit log (flat files)
• indexed and written in memtables (in-memory: write-back
cache)
• serialized to disk in a SSTable data file
• writes partitioned and replicated automatically in cluster
• SSTables consolidated though compaction to clean
tombstones
• repairs to ensure consistency cluster wide
34

cassandra.yaml: `cluster_name`
# The name of the cluster. This is mainly used to prevent machines in
# one logical cluster from joining another.
cluster_name: ‘my little cluster'
36

cassandra.yaml: `num_tokens`
# This defines the number of tokens randomly assigned to this node on the ring
# The more tokens, relative to other nodes, the larger the proportion of data
# that this node will store. You probably want all nodes to have the same number
# of tokens assuming they have equal hardware capability.
#
# If you leave this unspecified, Cassandra will use the default of 1 token for legacy
compatibility,
# and will use the initial_token as described below.
#
# Specifying initial_token will override this setting on the node's initial start,
# on subsequent starts, this setting will apply even if initial token is set.
#
# If you already have a cluster with 1 token per node, and wish to migrate to
# multiple tokens per node, see http://wiki.apache.org/cassandra/Operations
num_tokens: 256
37

cassandra.yaml: `partitioner`
# The partitioner is responsible for distributing groups of rows (by
# partition key) across nodes in the cluster. You should leave this
# alone for new clusters. The partitioner can NOT be changed without
# reloading all data, so when upgrading you should set this to the
# same partitioner you were already using.
#
# Besides Murmur3Partitioner, partitioners included for backwards
# compatibility include RandomPartitioner, ByteOrderedPartitioner, and
# OrderPreservingPartitioner.
#
partitioner: org.apache.cassandra.dht.Murmur3Partitioner
38

cassandra.yaml: `data_file_directories`
# Directories where Cassandra should store data on disk. Cassandra
# will spread data evenly across them, subject to the granularity of
# the configured compaction strategy.
# If not set, the default directory is $CASSANDRA_HOME/data/data.
data_file_directories:
- /var/lib/cassandra/data
39

cassandra.yaml: `commitlog_directory`
# commit log. when running on magnetic HDD, this should be a
# separate spindle than the data directories.
# If not set, the default directory is $CASSANDRA_HOME/data/commitlog.
commitlog_directory: /mnt/cassandra/commitlog
40

cassandra.yaml: `commitlog_compression`
# Compression to apply to the commit log. If omitted, the commit log
# will be written uncompressed. LZ4, Snappy, and Deflate compressors
# are supported.
#commitlog_compression:
# - class_name: LZ4Compressor
# parameters:
# -
41

cassandra.yaml: `disk_failure_policy`
# policy for data disk failures:
# die: shut down gossip and client transports and kill the JVM for any fs errors or
# single-sstable errors, so the node can be replaced.
# stop_paranoid: shut down gossip and client transports even for single-sstable errors,
# kill the JVM for errors during startup.
# stop: shut down gossip and client transports, leaving the node effectively dead, but
# can still be inspected via JMX, kill the JVM for errors during startup.
# best_effort: stop using the failed disk and respond to requests based on
# remaining available sstables. This means you WILL see obsolete
# data at CL.ONE!
# ignore: ignore fatal errors and let requests fail, as in pre-1.2 Cassandra
disk_failure_policy: stop
42

cassandra.yaml: `commit_failure_policy`
# policy for commit disk failures:
# die: shut down gossip and Thrift and kill the JVM, so the node can be replaced.
# stop: shut down gossip and Thrift, leaving the node effectively dead, but
# can still be inspected via JMX.
# stop_commit: shutdown the commit log, letting writes collect but
# continuing to service reads, as in pre-2.0.5 Cassandra
# ignore: ignore fatal errors and let the batches fail
commit_failure_policy: stop
43

cassandra.yaml: `seed_provider`
# any class that implements the SeedProvider interface and has a
# constructor that takes a Map<String, String> of parameters will do.
seed_provider:
# Addresses of hosts that are deemed contact points.
# Cassandra nodes use this list of hosts to find each other and learn
# the topology of the ring. You must change this if you are running
# multiple nodes!
- class_name: org.apache.cassandra.locator.SimpleSeedProvider
parameters:
# seeds is actually a comma-delimited list of addresses.
# Ex: "<ip1>,<ip2>,<ip3>"
- seeds: "10.239.206.80,10.243.206.82,10.238.206.80,10.241.206.80,10.240.206.80,10.244.206.80"
44

cassandra.yaml: `concurrent_*`
# For workloads with more data than can fit in memory, Cassandra's
# bottleneck will be reads that need to fetch data from
# disk. "concurrent_reads" should be set to (16 * number_of_drives) in
# order to allow the operations to enqueue low enough in the stack
# that the OS and drives can reorder them. Same applies to
# "concurrent_counter_writes", since counter writes read the current
# values before incrementing and writing them back.
#
# On the other hand, since writes are almost never IO bound, the ideal
# number of "concurrent_writes" is dependent on the number of cores in
# your system; (8 * number_of_cores) is a good rule of thumb.
concurrent_reads: 64
concurrent_writes: 128
concurrent_counter_writes: 32
45

cassandra.yaml: `listen_address`
# If you choose to specify the interface by name and the interface has an ipv4
and an ipv6 address
# you can specify which should be chosen using listen_interface_prefer_ipv6. If
false the first ipv4
# address will be used. If true the first ipv6 address will be used. Defaults to
false preferring
# ipv4. If there is only one address it will be selected regardless of ipv4/ipv6.
listen_address: 10.243.206.80
# listen_interface: eth0
# listen_interface_prefer_ipv6: false
46

cassandra.yaml: `native_transport_port`
# Whether to start the native transport server.
# Please note that the address on which the native transport is bound
is the
# same as the rpc_address. The port however is different and specified
below.
start_native_transport: true
# port for the CQL native transport to listen for clients on
# For security reasons, you should not expose this port to the
internet. Firewall it if needed.
native_transport_port: 9042
47

cassandra.yaml: `snapshot_before_compaction`
# Whether or not to take a snapshot before each compaction. Be
# careful using this option, since Cassandra won't clean up the
# snapshots for you. Mostly useful if you're paranoid when there
# is a data format change.
snapshot_before_compaction: false
48

cassandra.yaml: `auto_snapshot`
# Whether or not a snapshot is taken of the data before keyspace truncation
# or dropping of column families. The STRONGLY advised default of true
# should be used to provide data safety. If you set this flag to false, you will
# lose data on truncation or drop.
auto_snapshot: true
49

cassandra.yaml: `concurrent_compactors`
[…]
concurrent_compactors: 8
[…]
50

cassandra.yaml:
`compaction_throughput_mb_per_sec`
[…]
compaction_throughput_mb_per_sec: 16
[…]
51

cassandra.yaml:
`inter_dc_stream_throughput_outbound_megabits_per_sec`
[…]
# inter_dc_stream_throughput_outbound_megabits_per_sec: 200
[…]
52

cassandra.yaml: `*timeout*`
read_request_timeout_in_ms: 5000
range_request_timeout_in_ms: 10000
write_request_timeout_in_ms: 2000
counter_write_request_timeout_in_ms: 5000
cas_contention_timeout_in_ms: 1000
truncate_request_timeout_in_ms: 60000
# The default timeout for other, miscellaneous operations
request_timeout_in_ms: 10000
53

cassandra.yaml:
`streaming_socket_timeout_in_ms`
# Enable socket timeout for streaming operation.
# When a timeout occurs during streaming, streaming is retried from the start
# of the current file. This _can_ involve re-streaming an important amount of
# data, so you should avoid setting the value too low.
# Default value is 3600000, which means streams timeout after an hour.
# streaming_socket_timeout_in_ms: 3600000
54

cassandra.yaml: `endpoint_snitch`
# You can use a custom Snitch by setting this to the full class name
# of the snitch, which will be assumed to be on your classpath.
endpoint_snitch: SimpleSnitch
55

cassandra.yaml: `internode_compression`
# internode_compression controls whether traffic between nodes is
# compressed.
# can be: all - all traffic is compressed
# dc - traffic between different datacenters is compressed
# none - nothing is compressed.
internode_compression: all
56

cassandra.yaml: `gc_warn_threshold_in_ms`
# GC Pauses greater than gc_warn_threshold_in_ms will be logged at WARN level
# Adjust the threshold based on your application throughput requirement
# By default, Cassandra logs GC Pauses greater than 200 ms at INFO level
gc_warn_threshold_in_ms: 1000
57

cassandra.yaml: `hints*`
max_hints_delivery_threads: 2
# Directory where Cassandra should store hints.
# If not set, the default directory is $CASSANDRA_HOME/data/hints.
# hints_directory: /var/lib/cassandra/hints
# Compression to apply to the hint files. If omitted, hints files
# will be written uncompressed. LZ4, Snappy, and Deflate compressors
# are supported.
#hints_compression:
# - class_name: LZ4Compressor
# parameters:
# -
58

CMS vs G1
• CMS still default in 3.0.x
• CMS harder to tune for best performances but more stable / well known
• G1 still considered experimental w/ Cassandra 3.0.x
• G1 brings higher read throughout (~10%)
• G1 brings more constant performance (GC time)
• G1 can bring instability and OOM with heavy Cassandra operations
60

HEAP size
• -Xmx / -Xms: set same value
• CMS: 1/4 of RAM if RAM > 8G; no more than around 8G
• G1: a lot more…
• do not go crazy on HEAP size
61

(CMS) NEW_HEAP settings
NEW_HEAP: 20-25% of HEAP (max 50%)
keep low to keep GC pauses low (100MB per core)
62

useful settings for any (parallel) GC (1/2)
# The JVM maximum is 8 PGC threads and 1/4 of that for ConcGC.
# Machines with > 10 cores may need additional threads.
# Increase to <= full cores (do not count HT cores).
#JVM_OPTS="$JVM_OPTS -XX:ParallelGCThreads=16"
#JVM_OPTS="$JVM_OPTS -XX:ConcGCThreads=16"
63

useful settings for any (parallel) GC (2/2)
# Do reference processing in parallel GC.
JVM_OPTS="$JVM_OPTS -XX:+ParallelRefProcEnabled"
64

Where is the JVM configuration?
• < 3.0.0: cassandra-env.sh
• >= 3.0.0: jvm.options
65

enabling G1GC for C* < 3.0.0 (1/2)
# Use the Hotspot garbage-first collector.
JVM_OPTS="$JVM_OPTS -XX:+UseG1GC"
# Main G1GC tunable: lowering the pause target will lower throughput and vise versa.
# 200ms is the JVM default and lowest viable setting
# 1000ms increases throughput. Keep it smaller than the timeouts in cassandra.yaml.
JVM_OPTS="$JVM_OPTS -XX:MaxGCPauseMillis=500"
# Have the JVM do less remembered set work during STW, instead
# preferring concurrent GC. Reduces p99.9 latency.
JVM_OPTS="$JVM_OPTS -XX:G1RSetUpdatingPauseTimePercent=5"
# Start GC earlier to avoid STW.
# The default in Hotspot 8u40 is 40%.
JVM_OPTS="$JVM_OPTS -XX:InitiatingHeapOccupancyPercent=25"
# For workloads that do large allocations, increasing the region
66

enabling G1 for C* < 3.0.0 (2/2)
• comment out all CMS related lines in cassandra-env.sh
• comment out the -Xmn line
67

GC logging
• you should always enable GC logging
• safe on production with log rotation
68

the nodetool utility (1/2)
• command line interface for managing a cluster.
• nodetool [options] command [args]
nodetool help
nodetool help command name
• use Salt Stack (or equivalent) to get command results
coming from all nodes.
70

the nodetool utility (2/2)
nodetool info
nodetool version
nodetool status <ks>
nodetool describecluster
nodetool ring
nodetool tpstats
nodetool compactionstats
nodetool netstats
71
nodetool gcstats
nodetool clearsnapshot
nodetool rebuild
nodetool bootstrap (resume)
nodetool compact <ks> <cf>
nodetool drain
nodetool repair
nodetool upgradesstables

the SSTable utility
• sstable*
• dump / scrub / split / repair / upgrade etc.
72

the cassandra-stress tool
• stress testing utility for basic benchmarking and load
testing a Cassandra cluster
73

single node
• SimpleStrategy
• RF=1
75

cqlsh> CREATE KEYSPACE my_ks WITH
replication = {'class':
'SimpleStrategy', 'replication_factor':
‘1’};
76

extending a single datacenter
• NetworkTopologyStrategy
• RF=1
77

ALTER KEYSPACE my_ks WITH REPLICATION =
{'class' : 'NetworkTopologyStrategy',
‘east-dc' : 1};
78

cassandra-rackdc.properties (GossipingPropertyFileSnitch)
# These properties are used with GossipingPropertyFileSnitch and will
# indicate the rack and dc for this node
dc=east-dc
rack=rack1
79

cassandra-topology.properties (PropertyFileSnitch)
# Cassandra Node IP=Data Center:Rack
192.168.1.100=east-dc:rack1
80

adding a node to a datacenter (1/3)
• install Cassandra on the new nodes, but do not start Cassandra (if it starts
stop and delete all the data)
• setup snitch cassandra-topology.properties or cassandra-rackdc.properties or
nothing if RackInferringSnitch
• cassandra.yaml properties:
• auto_bootstrap: true (for non-seed nodes)
• cluster_name
• listen_address / broadcast_address
• endpoint_snitch (your choice of snitch)
• seed_provider: (seed nodes do not bootstrap. Make sure it is not in there)
81

dc=east-dc
rack=rack1
82

192.168.1.100=east-dc:rack1
192.168.1.101=east-dc:rack1
83

84
‘east-dc' : 2};

• start the new node
• check system.log for errors
• $ nodetool status (should be marked as UJ until UN)
• can take a while depending on the amount of data
• `streaming_socket_timeout_in_ms`
• `stream_throughput_outbound_megabits_per_sec`
• $ nodetool netstats
• $ nodetool bootstrap resume
85

adding a datacenter to a cluster (1/3)
• auto_bootstrap: false (first is seed node)
• same properties and config files as in adding a new node
• add that new node IP to the seed_provider in every
nodes configuration
• make sure your app uses LOCAL_QUORUM
86

dc=west-dc
rack=rack1
87

192.168.1.100=east-dc:rack1
192.168.1.101=east-dc:rack1
192.168.2.100=west-dc:rack1
88

89
‘east-dc' : 2, ‘west-dc’: 2};

• $ nodetool rebuild -- name_of_existing_data_center
• $nodetool netstats
• check for errors
• `streaming_socket_timeout_in_ms`
• `inter_dc_stream_throughput_outbound_megabits_per_sec`
• when done: auto_bootstrap: false
• seed of new DC is up and running you can now add more
90

replacing / decommissioning a dead node
• $ nodetool decommission
• $ nodetool removenode
• $ nodetool assassinate
• replacing a dead node
cassandra-env.sh
JVM_OPTS="$JVM_OPTS -Dcassandra.replace_address=address_of_dead_node
• do not forget to remove IP addresses snitch files
• need to promote another seed node by adding another IP to
seed_provider
91

decommissioning a datacenter
• ensure no clients writes to datacenter
• run full repair
• alter keyspace and remove datacenter 
ALTER KEYSPACE my_ks WITH REPLICATION = {'class' :
'NetworkTopologyStrategy', ‘east-dc' : 2};
• $ nodetool decommission for every node in the datacenter
getting decommission
92

deleting
• hard to delete w/ distributed systems
keeping track of replicas is hard and SSTables are immutable
• tombstones (data are not deleted quite yet)
removed when performing major compactions
repairs required before grace period (`gc_grace_seconds`: 10 days by
default; per table setting)
• truncate does not generate tombstones
• use TTL on tables
• copy to new table and drop old table easier / faster
93

compactions
• process of merging SSTables to single files
• IO heavy: GC / CPU / eat disk space)
• removes tombstones
• manual or automatic
• STCS: SizeTiercedCompactionStrategy
• DTCS: DateTiercedCompactionStrategy
• LCS: LeveledCompactionStrategy
• monitor logs for tombstones warnings (indicates compaction issue)
94

repairs
• Anti-Entropy: QUORUM & ALL replicas compared for CF and discrepancies
fixed.
• must run before `gc_grace_period` (10 days)
• repair running against token ranges from a coordinator node
• nodetool repair
• nodetool repair -pr (on every node in every datacenter)
• incremental repair (default in C* >= 2.2)
nodetool repair -inc (2.1)
• anticompaction
separation of repaired / unrepaired in different SSTables)
95

hints
• if node down: spool and redelivery
• slow and broken until 3.0: must truncate manually as
some are left off
• < 3.0: SSTables (which means compactions)
• >=3.0 flat files with compressions
96

upgrade (1/2)
• See DataStax Upgrade Guide
http://docs.datastax.com/en/latest-upgrade/upgrade/
cassandra/
upgradeCassandraDetails.html#upgradeCassandraDetails
97

upgrade (2/2)
• start with new config files and forward your changes
• no new features, no truncate and no repairs when
cluster using multiple versions
• read NEWS.txt and CHANGES.txt for specific instructions
• will show schema disagreement (normal)
• check log files
• $ nodetool upgradesstables
98

proper shutdown of a node
$nodetool disablethrift
$nodetool disablegossip
$nodetool drain
$service cassandra stop
99

dealing with SSTables corruptions

detecting corruption
• log files: /var/log/cassandra/system.log
• monitor logs: compaction errors, repairs errors can show corruptions
• cassandra.yaml: `disk_failure_policy`
101

cassandra.yaml: `disk_failure_policy`
• `stop` or `stop paranoid` dangerous when running cross-
DC repairs with failures
• do not use it on all nodes in a DC to make sure quorum is
still met in case of repairs or other failures
102

how to fix?
• when node is online: (verify you have space on disk for a snapshot of <CF>)
$ nodetool scrub <KS> <CF>
• if corruption persists, bring node offline and then:
$ sstablescrub <KS> <CF> 
then bring the node back up
• if corruption still persists bring the node down, remove the corrupted SSTables (no
need for backups since `scrub` kept a snapshot)
• start the node back up and run a repair 
$ nodetool repair <KS> <CF>
• verify that logs are cleared out
• $ nodetool clearsnapshot
103

look for
• read & write latency (cluster wide, per DC)
• read / write throughput monitoring
• pending operations (reads / writes / compactions)
RowMutationStage / ReadStage / CompactionStage
• general OS monitoring (CPU and DISK especially)
• GC collection time and size
• network traffic is throttled and configurable
105

Datastax OpsCenter
• Cassandra specific
• great tool
• free / commercial with goodies
• support for Open Source Cassandra until 2.1.x
• no alerting w/ free version
• uses Cassandra as backend
106

Graphite
• using JMX available metrics
• do it yourself
• lots of work but fine tuning
• choice of frontends (graphite-web, grafana)
• Cyanite (Cassandra backend)
107

log files
• system.log
• jvm.logs
• standard syslog monitoring
< 2.1 /etc/cassandra/log4j-server.properties
>=2.1 /etc/cassandra/logback.xml
108

SaaS monitoring
• Sematext
• DatadogHQ
• etc.
• agent-based
109

Cassandra 2.1.x
• most stable release so far
• streaming nodes can be an issue
• multi-DC repairs painful w/ 256 tokens(inc repairs mostly broken)
• hints delivery slow or broken
• 2.0.x to 2.1.x migration is smooth
• hardware ++ when migrating from 2.0.x to 2.1.x
• 2.1.x EOL 10/2016
111

Cassandra 2.2.x
• streaming got better (nodetool bootstrap resume)
• commit logs compression introduced
• incremental repairs is now the default (but still painful with 256 tokens…)
• hints delivery still slow or broken
• new 3.0 driver compatible.
• Datastax OpsCenter not compatible for C* >= 2.2
• 2.1.x to 2.2.x migration is smooth
• 2.1.x to 2.2.x or 3.0.x?
• 2.2.x EOL 10/2016
112

Cassandra 3.0.x
• new storage engine and major disk space savings
• hints storage (fs based) delivery / compression
• hints delivery new options (disablehintsfordc / enablehintsfordc)
• repairs still painful w/ 256 tokens…
• nodetool SSL support
• MS Windows support…
• require new driver
• community started migrating around March - April
• still expect some issues
• 3.0.0 EOL 09/2017
113

notes about storage
• Storage area network (SAN) storage is not
recommended for on-premises deployments
• Network attached storage (NAS) device is not
recommended
• NFS is not recommended
• unless you really know what you are doing :-)
114

SSD vs spinning disks vs flash array?
• you can do a lot w/ spinning disks
• weak for heavy IO operations such as SSTable migration
and repairs depending on workload
• if lots more reads than writes at application level hybrid
(SSD accelerated) performs great
• writes will not the the bottleneck (modulo operations above)
• iland is in the process of benchmarking Nimble flash array
115

keyspaces and tables
• 1 table ~ 1MB of memory (1k tables ~ 1GB)
• too many keyspaces / tables will bloat your memory
• shot for 500 tables per cluster (C* doc)
• max 1k (C* doc)
116

Linux settings
• disable swap (swapoff —all; /etc/fstab)
• verify user limits (should be the case with C* distro)
ulimit -a
• see Al’s Tobey’s C* 2.1 guide for XFS and hardware /
disks related tricks
117

must reads
• Datastax Apache Cassandra “official” documentation
• http://docs.datastax.com/en//cassandra/3.0/cassandra/
cassandraAbout.html
• Al's Cassandra 2.1 tuning guide
• https://tobert.github.io/pages/als-cassandra-21-tuning-guide.html
• cassandra-user mailing list
• http://www.planetcassandra.org/apache-cassandra-mailing-lists/
• planet Cassandra
• http://www.planetcassandra.org/
118

Cassandra multi-datacenter operations essentials

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