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5 Levels of High Availability
From Multi-instance to Hybrid Cloud
Rafał Leszko
@RafalLeszko
rafalleszko.com
Hazelcast
About me
● Cloud Software Engineer at Hazelcast
● Worked at Google and CERN
● Author of the book "Continuous Delivery
with Docker and Jenkins"
● Trainer and conference speaker
● Live in Kraków, Poland
About Hazelcast
● Distributed Company
● Open Source Software
● 140+ Employees
● Products:
○ Hazelcast IMDG
○ Hazelcast Jet
○ Hazelcast Cloud
@Hazelcast
● Introduction
● High Availability Levels
○ Level 0: Single Instance
○ Level 1: Multi Instance
○ Level 2: Multi Zone
○ Level 3: Multi Region
○ Level 4: Multi Cloud
○ Level 5: Hybrid Cloud
● Summary
Agenda
Introduction
application service
micro-service
application service
micro?
application service
application service
application service
5 levels of high availability  from multi instance to hybrid cloud
application service
Stateless
5 levels of high availability  from multi instance to hybrid cloud
application service
application servicedata store
application servicedata store
queue
application servicedata store
queue
other service
Data is the problem!
● Introduction ✔
● High Availability Levels
○ Level 0: Single Instance
○ Level 1: Multi Instance
○ Level 2: Multi Zone
○ Level 3: Multi Region
○ Level 4: Multi Cloud
○ Level 5: Hybrid Cloud
● Summary
Agenda
Level 0: Single Instance
application service data store
Level 0: Single Instance
machine
request
Level 0: Single Instance
YOLO!
LATENCY EXPERIMENT
5 levels of high availability  from multi instance to hybrid cloud
What does "Level 0: Single Instance" mean to You?
No high availability!
No scalability!
Super low latency:
● in-process memory
● no network
● local file system
Data consistency
● Introduction ✔
● High Availability Levels
○ Level 0: Single Instance ✔
○ Level 1: Multi Instance
○ Level 2: Multi Zone
○ Level 3: Multi Region
○ Level 4: Multi Cloud
○ Level 5: Hybrid Cloud
● Summary
Agenda
Level 1: Multi Instance
If one machine is down,
the system is still available
application
data
Level 1: Multi Instance
request
data
load balancer
application
application
application
application
machine 1
machine 2
machine 3
machine 4
application
data
Level 1: Multi Instance
data
application
application
application
application
machine 1
machine 2
machine 3
machine 4
data
Level 1: Multi Instance
data
machine 3
machine 4
data store
Level 1: Multi Instance
machine 1
data store
machine 2
Assumptions:
● Local network
● Fast
● Reliable
For example:
● EC2 Instances in the
same availability
zone
● GCP VM instances in
the same zone
● Your on-premises
server machines
connected with LAN
5 levels of high availability  from multi instance to hybrid cloud
data store
Level 1: Multi Instance
machine 1
data store
machine 2
Data replication
data store
Option 1: Active-Passive (Master-Slave) Replication
machine 1
data store
machine 2
application service
application service
application service
active
passive
SQL
data store
Option 1: Active-Passive (Master-Slave) Replication
machine 1
data store
machine 2
application service
application service
application service
active
passive
data store
Option 1: Active-Passive (Master-Slave) Replication
machine 1
data store
machine 2
application service
application service
application service
down
active
data store
Option 1: Active-Passive (Master-Slave) Replication
machine 1
data store
machine 2
application service
application service
application service
active
passive
SQL
data store
[A-G]
Option 2: Clustering
machine 1
data store
[H-S]
machine 2
data store
[T-Z]
machine 3
NoSQL
data store
[A-G]
Option 2: Clustering
machine 1
data store
[H-S]
machine 2
application service
application service
application service
data store
[T-Z]
machine 3
data store
[A-G]
Option 2: Clustering
machine 1
data store
[H-S]
machine 2
application service
application service
application service
data store
[T-Z]
machine 3
1
Hazelcast Member 1
data
partitions
4
7
data
partition
backups
3 5
9
3
Hazelcast Member 3
data
partitions
6
9
data
partition
backups
2 4
8
2
Hazelcast Member 2
data
partitions
5
8
data
partition
backups
1 6
7
data store
[A-G]
Option 2: Clustering
machine 1
data store
[H-S]
machine 2
data store
[T-Z]
machine 3
NoSQL
Synchronous
vs
Asynchronous
Synchronous (Consistency) or Asynchronous (Latency)?
data
store
machine 1
machine 2 machine 3
data
store
machine 1
data
store
machine 2
active
passive
data
store
data
store
LATENCY EXPERIMENT
5 levels of high availability  from multi instance to hybrid cloud
5 levels of high availability  from multi instance to hybrid cloud
Synchronous (Consistency) or Asynchronous (Latency)?
data
store
machine 1
machine 2 machine 3
data
store
machine 1
data
store
machine 2
active
passive
data
store
data
store
synchronous
Synchronous (Consistency) or Asynchronous (Latency)?
data
store
machine 1
machine 2 machine 3
data
store
machine 1
data
store
machine 2
active
passive
data
store
data
store
synchronous?
What does "Level 1: Multi Instance" mean to You?
Data consistency!
Most tools supported
Cloud-specific toolkit (e.g. AWS SQS)
Simple setup (even on-premises)
High latency if accessed multi regions
● Introduction ✔
● High Availability Levels
○ Level 0: Single Instance ✔
○ Level 1: Multi Instance ✔
○ Level 2: Multi Zone
○ Level 3: Multi Region
○ Level 4: Multi Cloud
○ Level 5: Hybrid Cloud
● Summary
Agenda
Level 2: Multi Zone
If one availability zone is down,
the system is still available
5 levels of high availability  from multi instance to hybrid cloud
application
data
Level 2: Multi Zone
request
data
load balancer
application
application
application
application
zone 1
zone 2
Is multi-zone deployment any
different?
No
No… but Yes
LATENCY EXPERIMENT
5 levels of high availability  from multi instance to hybrid cloud
No… but Yes
Level 2: Multi Zone
zone 1
zone 2
data data
data data
Level 2: Multi Zone
zone 1
zone 2
data data
data data
Assumptions:
● Machines in at
least 2 AZ
● Fast and
reliable
network
For example:
● EC2 Instances
in 2 AWS
Availability
Zones
● Azure VM
instances in 2
Availability
Sets
1
Hazelcast Member 1
data
partitions
4
7
data
partition
backups
3 5
9
3
Hazelcast Member 3
data
partitions
6
9
data
partition
backups
2 4
8
2
Hazelcast Member 2
data
partitions
5
8
data
partition
backups
1 6
7
Level 2: Multi Zone
machine 1 machine 2
Hazelcast Member 2
zone 1
zone 2
Hazelcast Member 1
machine 3 machine 4
Hazelcast Member 4Hazelcast Member 3
Hazelcast configuration:
hazelcast:
partition-group:
enabled: true
group-type: ZONE_AWARE
Hazelcast Zone Aware Feature
Hazelcast Zone Aware Feature
Level 2: Multi Zone
machine 1 machine 2
Hazelcast Member 2
zone 1
zone 2
Hazelcast Member 1
machine 3 machine 4
Hazelcast Member 4Hazelcast Member 3
No… but Yes
Make sure your
data store is
ZONE AWARE
What does "Level 2: Multi Zone" mean to You?
Currently top 1 choice!
Data consistency!
Cloud-specific toolkit (e.g. AWS SQS)
High latency if accessed multi regions
Not all tools are "zone aware"
● Introduction ✔
● High Availability Levels
○ Level 0: Single Instance ✔
○ Level 1: Multi Instance ✔
○ Level 2: Multi Zone ✔
○ Level 3: Multi Region
○ Level 4: Multi Cloud
○ Level 5: Hybrid Cloud
● Summary
Agenda
Level 3: Multi Region
If one region is down,
the system is still available
application
data
Level 3: Multi Region
geo
load balancer
region 1
load balancer
load balancer
region 2
application
application
application
application
application
application
application
data
data
data
data
data
geo replication
data
Level 3: Multi Region
region 1
region 2
data
data
data
data
data
geo replication
Assumptions:
● Machines in at
least 2
geographical
regions
● Network may be
slow and unreliable
For example:
● EC2 Instances in
regions: eu-central-
1 and us-west-2
10 000 km
Speed of light: 300 000 km/s
Distance: 10 000 km
RTT (Round Trip Time) = 60 ms
Level 3: Multi Region
Geo-replication
data
data
data
geo replication
Level 3: Multi Region (Geo-replication)
data
data
data
Geo-replication
● It's asynchronous
● Your data store must support it
● You must be prepared for data loss
● Two modes:
○ Active-Passive
○ Active-Active
data
data
data
geo replication
Active-Passive Geo-replication
data
data
data
active passive
data
data
data
geo replication
Active-Passive Geo-replication
data
data
data
active passive
● data loss possible
● (eventual) consistency
data
data
data
geo replication
Active-Active Geo-replication
data
data
data
active active
data
data
data
geo replication
Active-Active Geo-replication
data
data
data
active active
● data loss possible
● eventual consistency
● conflict resolution
Hazelcast WAN Replication
hazelcast:
wan-replication:
batch-publisher:
target-endpoints: 35.184.122.109
Do I really need to lose
consistency?
LATENCY EXPERIMENT
5 levels of high availability  from multi instance to hybrid cloud
5 levels of high availability  from multi instance to hybrid cloud
5 levels of high availability  from multi instance to hybrid cloud
Strong Consistency in Multi Region
● NewSQL (Spanner, CockroachDB)
● Multi-region distributed transactions
● Consensus algorithms (Paxos, Raft)
● Always a trade-off: consistency vs latency
What does "Level 3: Multi Region" mean to You?
Super high available!
Low latency if accessed from multi regions
Sometimes possible to use Cloud-specific
toolkit (e.g. Google Spanner - yes, AWS
Elasticache - no)
Geo-replication (asynchronous)!
Eventual consistency (conflict resolution)
● Introduction ✔
● High Availability Levels
○ Level 0: Single Instance ✔
○ Level 1: Multi Instance ✔
○ Level 2: Multi Zone ✔
○ Level 3: Multi Region ✔
○ Level 4: Multi Cloud
○ Level 5: Hybrid Cloud
● Summary
Agenda
Level 4: Multi Cloud
If one cloud provider is down,
the system is still available
app
data
Level 4: Multi Cloud
global
load balancer
load
balancer
app
app
data
data
replication
app
data
load
balancer
app
app
data
data
data
Level 4: Multi Cloud
data
data
replication
data
data
data
cloud provider 1
cloud provider 2
Assumptions:
● Machines in at
least 2 cloud
providers
● Network may be
slow and unreliable
● Machines may be
in different geo
regions
For example:
● EC2 Instances in
eu-central-1 and
GCP VM Instances
in us-west1-a
What's different from multi-
region?
Level 4: Multi Cloud
● No Cloud-specific tools
● No VPC Peering across Cloud providers
○ Latency
○ Security
● Cost
Is High Availability the only
reason for Multi-Cloud?
Reasons for Multi-Cloud
● High Availability / Disaster Recovery
● Avoiding vendor lock-in
● Cloud cost optimization
● Risk Mitigation
● Low latency
● Data Protection / Regulations / Compliance
● Best-Fit Technology (Cloud-specific portfolios)
What does "Level 4: Multi Cloud" mean to You?
No vendor lock-in!
Cloud cost negotiations
Low latency if accessed from multi-cloud
Complex setup!
No Cloud toolkit (e.g. AWS SQS)
● Introduction ✔
● High Availability Levels
○ Level 0: Single Instance ✔
○ Level 1: Multi Instance ✔
○ Level 2: Multi Zone ✔
○ Level 3: Multi Region ✔
○ Level 4: Multi Cloud ✔
○ Level 5: Hybrid Cloud
● Summary
Agenda
Level 5: Hybrid Cloud
If all cloud providers are down,
the system is still available
5 levels of high availability  from multi instance to hybrid cloud
Is it possible that
all cloud providers
are down?
No!
Reasons for Hybrid Cloud
● Data requirements / regulations
● Data security
● Moving to Cloud
● Cost reduction
● All mentioned already in Multi-Cloud
Level 5: Hybrid Cloud
global
load balancer
On-Premises
5 levels of high availability  from multi instance to hybrid cloud
What does "Level 5: Hybrid Cloud" mean to You?
No Cloud lock-in!
Low latency if accessed from custom
networks
Super complex setup!
Usually extra layer needed (e.g.
Kubernetes, OpenShift)
Costs a fortune!
● Introduction ✔
● High Availability Levels
○ Level 0: Single Instance ✔
○ Level 1: Multi Instance ✔
○ Level 2: Multi Zone ✔
○ Level 3: Multi Region ✔
○ Level 4: Multi Cloud ✔
○ Level 5: Hybrid Cloud ✔
● Summary
Agenda
Summary
Single Instance Multi Instance Multi Zone Multi Region Multi Cloud Hybrid Cloud
distributed system
(data replication)
Single Instance Multi Instance Multi Zone Multi Region Multi Cloud Hybrid Cloud
distributed system
(data replication)
Single Instance Multi Instance Multi Zone Multi Region Multi Cloud Hybrid Cloud
zone aware
distributed system
(data replication)
Single Instance Multi Instance Multi Zone Multi Region Multi Cloud Hybrid Cloud
long distance
(geo-
replication)
zone aware
distributed system
(data replication)
Single Instance Multi Instance Multi Zone Multi Region Multi Cloud Hybrid Cloud
no cloud
tools
long distance
(geo-
replication)
zone aware
distributed system
(data replication)
Single Instance Multi Instance Multi Zone Multi Region Multi Cloud Hybrid Cloud
no cloud
tools
own
infrastructure
long distance
(geo-
replication)
zone aware
Which
High Availability Level
is for me?
Single Instance Multi Instance Multi Zone Multi Region Multi Cloud Hybrid Cloud
Single Instance Multi Instance Multi Zone Multi Region Multi Cloud Hybrid Cloud
Single Instance Multi Instance Multi Zone Multi Region Multi Cloud Hybrid Cloud
Single Instance Multi Instance Multi Zone Multi Region Multi Cloud Hybrid Cloud
Single Instance Multi Instance Multi Zone Multi Region Multi Cloud Hybrid Cloud
Rafał Leszko
@RafalLeszko
rafalleszko.com
Thank You!

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5 levels of high availability from multi instance to hybrid cloud