The document discusses four approaches to disaster recovery in AWS: 1. Backup and restore - Creates AMIs of servers and relies on automated backups of RDS databases stored in S3. Restoration can be slow. 2. Pilot light - Keeps a minimal secondary site running to reduce recovery time but at a higher cost than backup/restore. 3. Warm standby - Maintains a secondary site in a scaled-up state for testing, reducing recovery time further but at a higher cost than pilot light. 4. Multi-site - Fully replicates the primary site across availability zones or regions for the fastest recovery time but at a significantly higher cost than other options.

1. Disaster Recovery
Approaches

2. Approach 1 : Backup and Restore
Route 53
MySQL RDS –
Multi AZ
Availability Zone 1
Browser Access
Mobile Access
Web
Server
Optional
Snapshot/Full Backup
S3
AMI
• DR – For Servers – Create AMI
• DR – For RDS MySQL – Amazon maintains replica. Additionally - automated Backup OR Snapshot/backup stored in S3
Elastic IP
Auto Scaling group Auto Scaling group
App
Server
Backup Phase
Automated
Replication
MySQL RDS
Replica in
Other AZ
Availability Zone 1

3. Approach 1 : Backup and Restore
Route 53
MySQL RDS
Old MySQL DB
Mobile Access
Web
Server
AMI
Elastic IP
Auto Scaling group
Auto Scaling group
App
Server
Old Web Server
Old App Server
Web
Server
App
Server
Browser Access
• Bring Servers up using backed up AMIs
• DR – For RDS MySQL – Amazon promotes Replica as Master
Restore
Restore
Restore Phase
Availability Zone 1
Availability Zone 2
Replica Promoted
As Master

4.  Pros of Backup-Restore
 Cost effective solution as other than running cost, one pays only for storage charges
and S3 charges are as low as $ 0.01 per GB.
 Effective operational strategy as it has been tested over the years by the industry.
 Customized backup procedures can be written to suite particular business need.
 Cons of Backup-Restore
 Slow in restoration process when failure occurs. DB restoration can take time
depending on size of DB backup.

5. Approach 2 :Pilot Light (Preparation Phase)
Route 53
Database
Replication
Elastic IP
Auto Scaling group
Auto Scaling group
Liferay
App
Server 1
Tomcat
Web
Server 1
App
Server
Web
Server
Auto Scaling group
Auto Scaling group
App
Server
(Stopped)
Web
Server
(Stopped)
Availability Zone 1 Availability Zone 2
AMI
Replica
Browser Access
Mobile Access
• DR – For Servers using
AMIs
• DR – For RDS MySQL –
Amazon maintains
replica. Additionally -
automated Backup OR
Snapshot/backup
stored in S3

6. Approach 2 :Pilot Light (Recovery Phase)
Auto Scaling group
Auto Scaling group
Liferay
App
Server 1
Tomcat
Web
Server 1
App
Server
Web
Server
Auto Scaling group
Auto Scaling group
App
Server
(Running)
Web
Server
(Running)
Availability Zone 1
Availability Zone 2
Replica Promoted
As Master
Route 53
Elastic IP
Browser Access
Mobile Access
• Start stopped state
servers.
• DR – For RDS
MySQL – Amazon
promotes Replica
as Master

7. Pros of Pilot-Light
 Quick recovery time as compared to traditional backup and restore approach.
 Secondary site can be brought up using primary server images (AMI),
therefore no re-configuration for server/app is required.
 Multiple region setup help improve redundancy.
Cons of Pilot-Light
 Slightly costlier as compared to traditional backup and restore approach as in
addition to primary site, secondary database server is kept into a running
state.
 Bringing servers up and replica to master transition activity require some time
before application is back in business.

8. Approach3:Warm Standby (Preparation phase)
Route 53
Database
Replication
Elastic IP
Auto Scaling group
Auto Scaling group
Liferay
App
Server 1
Browser Access
Mobile Access
Tomcat
Web
Server 1
App
Server
Web
Server
Auto Scaling group
Auto Scaling group
App
Server
(Min Infra)
Web
Server
(Min Infra)
Availability Zone 1
Availability Zone 2
AMI
Replica
• DR – For Servers using
AMIs
• DR – For RDS MySQL –
Amazon maintains
replica. Additionally -
automated Backup OR
Snapshot/backup
stored in S3

9. Approach3:Warm Standby (Recovery phase)
Route 53
Elastic IP
Auto Scaling group
Auto Scaling group
Liferay
App
Server 1
Browser Access
Mobile Access
Tomcat
Web
Server 1
App
Server
Web
Server
Auto Scaling group
Auto Scaling group
App
Server
(Scaled Up)
Web
Server
(Scaled Up)
Availability Zone 1
Availability Zone 2
Replica Promoted
As Master
• Scaled up min-infra
servers.
• DR – For RDS
MySQL – Amazon
promotes Replica
as Master

10. Pros of Warm-Standby
 As secondary site is always in up and running state, therefore downtime is
very less.
 Secondary site can be utilized for non-production activities, testing, internal
development usage etc., making optimal use of resources invested.
Cons of Warm-Standby
 Relatively higher cost as both primary and secondary sites are up and running.
 Since both primary and secondary sites initially points to primary database
server, one should be extra cautious of any updates being made through
secondary site which is meant for non-production activities during non-DR
phase.
 Scaling up server and replica to master transition activity require some time
before application is back in business.

11. Approach 4: Multi site (Preparation Phase)
Route 53
Database
Replication
Auto Scaling group
Auto Scaling group
Liferay
App
Server 1
Browser Access
Mobile Access
App
Server
Web
Server
Auto Scaling group
Auto Scaling group
App
Server
Web
Server
Availability Zone 1 Availability Zone 2
Replica
• DR – For Servers using
AMIs
• DR – For RDS MySQL –
Amazon maintains
replica. Additionally -
automated Backup OR
Snapshot/backup
stored in S3

12. Approach 4: Multi site (Recovery Phase)
Route 53
Auto Scaling group
Auto Scaling group
Liferay
App
Server 1
Browser Access
Mobile Access
App
Server
Web
Server
Auto Scaling group
Auto Scaling group
App
Server
Web
Server
Availability Zone 1 Availability Zone 2
Replica Promoted
As Master
• All traffic diverted
to secondary site.
• DR – For RDS
MySQL – Amazon
promotes Replica
as Master

13. Pros of Multi-site
 Robust DR mechanism as entire setup is replicated across two different
availability zones.
 To further enhance protection against DR, replication can be across regions.
 Full scaled setup enables business continuity with very less downtime.
Cons of Multi-site
 Significant higher cost for setup as full scaled deployment is setup in two
different locations.
 Similar to other few DR approaches, any data integrity loss at primary
database server may also affect data integrity at secondary database server.

14.  To have true Disaster Recovery in place, recommended approach is to have primary site and
secondary site in two Amazon regions e.g., one in US and another in Europe or Singapore.
However the complexity involved in such setup results in higher setup and maintenance cost.
Therefore we have considered multiple availability zone options within same region.
 Since availability zones are separate from each other in all terms, location, power supplier, cooling
services etc, they provide first line of defense against any disaster.
 Following diagram will help understand Region/Availability Zone concepts.
Notes
AWS Cloud
Europe Region
US East Region
Singapore Region
Availability
Zone
Availability
Zone
Availability
Zone
Availability
Zone
Availability
Zone
Availability
Zone
Availability
Zone
Availability
Zone
Availability
Zone